An Add-in is a chunk of code that is employed as a reusable augmentation to Excel. An Add-in might be implemented in a language like VB6 or more easily and commonly another Excel workbook containing some code that one might generally want to reuse. For example, it is practical and useful to reuse the DebugTools and EventLog modules from the Bulletproof.xls workbook in Chapter 7, so we might elect to add the Bulletproof.xls workbook to our list of Add-ins making it available to all future workbooks. In this chapter we will demonstrate how to make any workbook an Add-in, and as such, much more readily accessible to all workbooks.
Add-ins may but do not have to be compiled, external applications. However, since Office 2000 Developer Edition, support for compiling workbooks has been assisted. For more information on using compiled Add-ins refer to Chapter 13, Automation Add-ins and COM Add-ins.
In this chapter we will use the Bulletproof.xls workbook as an Add-in, and we will show you how to hide the implementation details of Add-in code to prevent it from being inadvertently changed by future consumers.
Workbooks are intellectual property. Workbooks used as Add-ins represent intellectual property that you may want to share or sell to other developers, but you may not necessarily want them to know the nuts and bolts of your solution. While you cannot prevent a consumer from knowing that your Add-in exists because it shows up in the Project ...