INTRODUCTIONIntroductionAbout This Book

Microsoft Excel is much more than just a spreadsheet. With the introduction of the Visual Basic Editor in Excel 97, followed by the significantly improved stability of Excel 2000, Excel became a respected development platform in its own right. Excel applications are now found alongside those based on C++, Java, and the .NET development platform, as part of the core suite of mission-critical corporate applications.

Unfortunately, Excel is still too often thought of as a hobbyist platform, that people only develop Excel applications in their spare time to automate minor tasks. A brief look at many Excel VBA books seems to confirm this opinion. These books focus on the basics of automating Excel tasks using VBA. This book is the first of its kind in providing a detailed explanation of how to use Excel as the platform for developing professional quality applications.

While most other major development platforms seem to have a de facto standard text that explains the commonly agreed best practices for architecting, designing, and developing applications using that platform, until now Excel has not. This book attempts to fill that gap. The authors are professional Excel developers who create Excel-based applications for clients ranging from individuals to the largest multinational corporations. This book explains the approaches we use when designing, developing, distributing, and supporting the applications we write for our clients.

Who Should Read This Book

This is not a beginner-level book. If you do not already have a clear understanding of the core Excel object model and a basic understanding of Excel VBA development this is not the place to start. We assume that readers of this book have already read and (mostly) understood our Excel 2002 or 2007 VBA Programmer’s Reference, John Walkenbach’s Excel Power Programming, or similar titles. This book begins where other Excel VBA books end.

Owners of the first edition of Professional Excel Development have a different decision to make. Should you purchase the second edition? We have made numerous corrections and improvements throughout this edition as well as expanding it with over 300 pages of new material that you simply will not find anywhere else.

In the interest of full disclosure, however, we want to be very clear that the bulk of the new material is aimed at Excel developers who are working with Excel 2007 and Visual Studio 2008. If you own the first edition of this book and your primary focus is developing VBA applications in Excel 2003 and earlier, you will see incremental rather than revolutionary improvements in this edition. We don’t want to discourage you from upgrading to the second edition and would welcome it if you choose to do so. But most of all we want you to be satisfied with our work, so we state the pros and cons of upgrading honestly to help you make an informed decision.

Excel Developer Categories

Excel developers can be divided into five general categories based on their experience and knowledge of Excel and VBA. This book has something to offer each of them, but with a focus on the more advanced topics. Putting yourself into one of these categories might help you decide whether this is the right book for you.

Basic Excel users probably don’t think of themselves as developers at all. Excel is no more than a tool to help them get on with their job. They start off using Excel worksheets as a handy place to store lists or perform simple repetitive calculations. As they discover more Excel features their workbooks may begin to include more complex worksheet functions, pivot tables, and charts. There is little in this book for basic Excel users, although Chapter 4, “Worksheet Design,” details the best practices to use when designing and laying out a worksheet for data entry; Chapter 20, “Data Manipulation Techniques,” explains how to structure a worksheet and which functions and features to use to manipulate their lists; and Chapter 21, “Advanced Charting Techniques,” explains how to get the most from Excel’s chart engine. The techniques suggested in these chapters should help the basic Excel user avoid some of the pitfalls often encountered as their experience and the complexity of their worksheets increase.

Excel power users have a broad understanding of Excel’s functionality and they know which tool or function is best used in a given situation. Power users create complex workbooks for their own use and are often called on to help develop workbooks for their colleagues, or to identify why their colleagues’ workbooks don’t work as intended. Power users occasionally use snippets of VBA, either found on the Internet or created with the macro recorder, but struggle to adapt the code to their needs. As a result, their code tends to be messy, slow, and hard to maintain. While this book is not a VBA tutorial, power users have much to gain from following the best practices we suggest for both worksheets and code modules. Most of the chapters in the book are relevant to power users who have an interest in improving their Excel and VBA development skills.

VBA developers make extensive use of VBA code in their workbooks—often too much. They are typically either power users who started to learn VBA too early or Visual Basic developers who switched to Excel VBA development. While they may be proficient with VBA they believe every problem must have a VBA solution. They tend to lack the experience required to know when a problem is best solved using Excel, when a problem is best solved using VBA, and when the best solution is a combination of the two. Their solutions are often cumbersome, slow, and make poor use of the Excel object model. This book has much to offer VBA developers to improve their use of Excel itself, including best practices for designing worksheets and how to use Excel’s features for data entry, analysis, and presentation. The book also seeks to improve their Excel VBA development skills by introducing advanced coding techniques, detailing VBA best practices, and explaining how to improve VBA code performance.

Excel developers realize that the most efficient and maintainable applications are those that make the most of Excel’s built-in functionality, augmented by VBA where appropriate. They are confident in developing Excel-based applications for their colleagues or as part of an in-house development team. While their knowledge of Excel is put to good use in their applications, their design techniques tend to be limited, and they are reluctant to use other languages and applications to augment their Excel solutions. They have probably read John Walkenbach’s Excel 2003 or 2007 Power Programming and/or our own Excel 2002 or 2007 VBA Programmer’s Reference. Now they need a book to take them to the highest level of Excel application development—that of the professional developer. This is the book to do that.

Professional Excel developers design and develop for their clients or employer Excel-based applications and utilities that are robust, fast, easy to use, maintainable, and secure. While Excel forms the core of their solutions, they use other applications and languages where appropriate, including third-party ActiveX controls, Office automation, Windows API calls, external databases, various standalone programming languages, and

Excel as an Application Development Platform

If we look at Excel as a development platform rather than just a spreadsheet, we find that it provides five fundamental components we can use in our applications:

• The worksheets, charts, and other objects used to create a user interface and presentation layer for data entry and reporting
• The worksheets used as simple data stores for lists, tables, and other information required by our application
• VBA code and UserForms for creating business logic and advanced user interfaces
• Worksheet formulas used as a declarative programming language for high-performance numerical processing
• The Excel object model, allowing programmatic control of (nearly) all of Excel’s functionality, both from within Excel and from outside it

Most people think about Excel in terms of typing numbers into cells, having some calculations update, and seeing a result displayed in a different cell or on a chart. Without necessarily thinking in such terms, they are using the worksheet as a user interface for their data entry and reporting and are generally comfortable with these tasks. The in-cell editing, validation, and formatting features built in to Excel provide a rich and compelling data entry experience, while the charting, cell formatting, and drawing tools provide a presentation-quality reporting mechanism.

It is hard to imagine the code that would be required if we tried to reproduce this experience using the tools available in most other development environments, yet Excel provides these features right out of the box for use in our Excel-based applications. The biggest problem we face is how to add structure to the free-form worksheet grid to present a simple and easy-to-use interface, while leveraging the rich functionality of Excel. Chapter 4 introduces some techniques and best practices for developing worksheet-based data entry forms, while Chapter 21 covers charting capabilities.

The Worksheet as a Simple Data Store

What is a worksheet when it’s never intended to be shown to the end user? At its simplest, it’s no more than a large grid of cells in which we can store just about anything we want, including numbers, text, lists, tables, and pictures. Most applications use some amount of static data or graphical resources. Storing that information in a worksheet makes it both easy to access using VBA and simple to maintain. Lists and tables in worksheets can directly feed Excel’s data validation feature (as shown in Chapter 4), greatly simplify the creation and maintenance of command bars (Chapter 8, “Advanced Command Bar Handling”), and allow us to construct dynamic UserForms (Chapter 13, “UserForm Design and Best Practices”).

VBA Code and UserForms

We expect most readers of this book have at least some familiarity with VBA. If not, we suggest you read one of the resources mentioned at the beginning of this chapter before continuing much further. Many people see the “A” in VBA as meaning the language is somehow less than Visual Basic itself. In fact, both VB6 and Office use exactly the same DLL to provide the keywords, syntax, and statements we program with.

Most beginner and intermediate VBA developers use VBA as a purely procedural language, with nearly all their code residing in standard modules. VBA also allows us to create applications using an object oriented programming (OOP) approach, in which class modules are used to create our own objects. Chapter 7, “Using Class Modules to Create Objects,” and Chapter 14, “Interfaces,” explain how to use VBA in this manner, while basic OOP concepts (such as encapsulation) are used throughout the book.

Most of this book is dedicated to explaining advanced VBA techniques and a professional approach to application design and development that can put VBA in Excel on par with, and sometimes in front of, VB6 or VB.Net for application development. In Chapters 23 through 26 we show that Excel developers can achieve the best of both worlds by combining Excel with VB6 or VB.Net in a seamless application.

The Worksheet as a Declarative Programming Language

Take the following code:

dSales = 1000dPrice = 10.99dRevenue = dSales
• dPrice

That could easily be a few lines of VBA. We give the variable dSales a value of 1000, the variable dPrice a value of 10.99, and then calculate the revenue as sales times price. If we change the names of the variables and adjust the spacing, the same code could also be written as

D1 =1000D2 =10.99D3 =D1*D2

This looks much more like worksheet cell addresses and formulas than lines of VBA code, showing that worksheet formulas are in fact a programming language of their own if we choose to think of it in those terms. The IF() worksheet function is directly equivalent to the If...Then...Else VBA statement, while the judicious use of circular references and iteration can be equivalent to either the For...Next or Do...Loop structures.

Instead of stating a set of operations that are executed line-by-line, we “program” in this language by making a set of declarations (by typing formulas and values into worksheet cells), in any order we want:

“D3 is the product of D1 and D2”

“D1 has the value 1000”

“D2 has the value 10.99”

To “run” this program, Excel first examines all the declarations and builds a precedence tree to identify which cells depend on the results of which other cells and thereby determine the most efficient order in which the cells must be calculated. The same precedence tree is also used to identify the minimum set of calculations that must be performed whenever the value in a cell is changed. The result is a calculation engine that is vastly more efficient than an equivalent VBA program, and one that should be used whenever complex numerical computations are required in your application.

Microsoft Excel is unique among application development platforms in providing both a procedural (VBA) and a declarative (worksheet functions) programming language. The most efficient Excel application is one that makes appropriate use of both these languages.

It is assumed the reader of this book has a basic understanding of worksheet functions, so Chapter 20 focuses on using advanced worksheet functions (including best-practice suggestions for handling circular references) and Excel’s other data analysis features.

The Excel Object Model

While the other four components of the Excel platform are invaluable in the development of applications, it is probably the rich Excel object model that provides the most compelling reason to base our applications in Excel. Almost everything that can be accomplished through the Excel user interface can also be accomplished programmatically using the objects in the Excel object model. (Accessing the list of number formats and applying a digital signature to a workbook are perhaps the most notable exceptions.)

The vast feature set exposed by these objects makes many complex applications fairly simple to develop. Unlike most other development platforms, there is no need to figure out how to program these features from scratch. Excel provides them ready-made, so all we need to do is determine how to plug them together most effectively. This book does not attempt to explore and document every obscure niche of the Excel object model. Instead, we demonstrate the best way to use the objects we most commonly use in our own application development.

Structure

Over the course of this book we cover both the concepts and details of each topic and apply those concepts to a time sheet reporting and analysis application that we will build in stages as we move along. The chapters are therefore arranged approximately in the order in which we would design and develop an Excel application:

• Chapter 2 discusses the different styles of application we might choose to create.
• Chapter 3 identifies some general best practices for working with Excel and VBA. These are followed throughout the book.
• Chapter 4 explains how to design and structure a worksheet for data entry and analysis.
• Chapters 5 and 6 introduce two specific types of application—the add-in and the dictator application, which form the basis of our time sheet reporting and analysis application.
• Chapter 7 introduces the use of class modules in our Excel applications.
• Chapters 8 to 11 discuss topics relevant to building command bar and Ribbon user interfaces as well as designing applications that must run in all current Excel versions using a single code base.
• Chapters 12 to 17 discuss advanced techniques for a range of VBA topics.
• Chapters 18 and 19 cover database development for Excel developers.
• Chapters 20 and 21 explain how to efficiently use Excel’s features to analyze data and present results.
• Chapters 22 to 27 look outside Excel, by explaining how to automate other applications and extend Excel with Visual Basic 6, VB.NET, and C.
• Chapter 28 focuses on how Excel applications can make use of Web Services.
• Chapter 29 completes the development by explaining how to provide help for, secure, and deploy an Excel application.

As mentioned previously, throughout the book, we illustrate the concepts and techniques we introduce by building a time sheet data entry, consolidation, analysis, and reporting application. This consists of a data entry template to be completed by each employee, with the data sent to a central location for consolidation, analysis, and reporting. At the end of most chapters we show an updated working example of the application that incorporates ideas presented in those chapters, so the application grows steadily more complex as the book progresses.

In Chapter 4, we start with a simple data entry workbook and assume that each employee would e-mail the completed file to a manager who would analyze the results manually—a typical situation for a company with just a few employees.

By the end of the book, the data entry workbook will use

Along the way we rewrite some parts of the application in a number of different ways to show how easy it can be to include other languages and delivery mechanisms in our Excel-based applications. Most chapters also include specific concept examples to illustrate key points that are important to understand but would be too artificial if forced into the architecture of our time sheet application.

Supported Versions of Excel

When we develop an Excel application for a client, that client’s upgrade policy usually determines the version of Excel we must use. Few clients agree to upgrade just so we can develop using the latest version of Excel unless there is a compelling business requirement that can only be satisfied by using features the latest version introduces. At the time of this writing, an extremely unscientific poll (based on postings to the Microsoft support newsgroups) seems to indicate the following approximate usage distribution for each current version of Excel:

There are still a small number of users on Excel 97 and earlier versions, but for various reasons we no longer consider these versions of Excel to be viable development platforms. We therefore decided to use Excel 2000 as our lowest supported version. Many features we discuss, especially when we cover

Typefaces

The following text styles are used in this book:

Menu items and dialog text are shown as Tools > Options > Calculation > Manual, where the “>” indicates navigation to a submenu or dialog tab.

Sub SomeCode() ‘Code listings are shown like thisEnd Sub

Code within the text of a paragraph is shown in a fixed-width font like Application.Calculation = xlManual.

Paths on the CD are shown as \Concepts\Ch14 - Interfaces.

New terms introduced or defined appear like this.

Important points or emphasized words appear like this.

On the CD

Most of the code listings shown in the book are also included in example workbooks on the accompanying CD. For clarity, the code shown in the printed examples may use shorter line lengths, reduced indent settings, fewer code comments, and less error handling than the corresponding code in the workbooks. The CD has three main directories, containing the following files:

• \Tools contains a number of tools and utilities developed by the authors that we have found to be invaluable during our application development. The MustHaveTools.htm file contains details about each of these tools and links to other third-party utilities.
• \Concepts has separate subdirectories for each chapter, each one containing example files to support the text of the chapter. For best results, we suggest you have these workbooks open while reading the corresponding chapter.
• \Application has separate subdirectories for the chapters where we have updated our time sheet example application. These chapters end with a Practical Example section that explains the changes made to implement concepts introduced in that chapter.

By far the best place to go for help with any of your Excel development questions, whether related to this book or not, are the Microsoft support newsgroup archives maintained by Google at http://groups.google.com. A quick search of the archives is almost certain to find a question similar to yours, already answered by one of the many professional developers who volunteer their time helping out in the newsgroups, including all the authors of this book. On the rare occasions that the archives fail to answer your question, you’re welcome to ask it directly in the newsgroups by connecting a newsreader (such as Outlook Express) to msnews."microsoft."com and selecting an appropriate newsgroup, such as

http://microsoft.public.excel.misc for general Excel questions

http://microsoft.public.excel.programming for VBA-related questions

http://microsoft.public.excel.worksheet.functions for help with worksheet functions

For assistance with Excel and VB.NET integration issues we recommend the MSDN VSTO Web forum located here:

http://social.msdn.microsoft.com/Forums/en-US/vsto/threads/

A number of Web sites provide a great deal of information and free downloadable examples and utilities targeted towards the Excel developer, including

http://www.appspro.com

http://www.excelkb.com

http://www.oaltd.co.uk

http://peltiertech.com

http://www.cpearson.com

http://msdn.microsoft.com/office

As an experiment for the second edition of Professional Excel Development, we are introducing a new Web site to accompany the book at http://www.ProExcelDev.net.

As of this writing the site does not yet exist, so it is difficult to say exactly what you will find there. However, at a minimum you will find the latest corrections, bug fixes, and clarifications related to this book. Our hope is to eventually expand the site to provide more in-depth coverage of popular topics than we were able to fit into our publishing deadline as well as blogs and possibly even interactive technical forums.

Feedback

We have tried very hard to present the information in this book in a clear and concise manner, explaining both the concepts and details needed to get things working as well as providing working examples of everything we cover. We have tried to provide sufficient information to enable you to apply these techniques in your own applications without getting bogged down in line-by-line explanations of entire code listings.

We’d like to think we’ve been successful in our attempt, but we encourage you to let us know what you think. Constructive criticism is always welcomed, as are suggestions for topics you think we may have overlooked. Please send feedback to the following authors:

Rob Bovey: robbovey@appspro.com

Dennis Wallentin: dennis@excelkb.com

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