This chapter shows you how to package Microsoft Excel worksheets, controls, menus, toolbars, and supporting Visual Basic modules in the form of an add-in application. You can use add-ins to assemble and distribute custom features that, from the user's point of view, act as if they're built into Microsoft Excel itself.
An add-in is a hidden, read-only workbook in which the Visual Basic code has been fully compiled from a source workbook. Because the code is already fully compiled, there is no compiler-induced delay when you run a procedure from an add-in. The add-in is hidden so that users can run procedures without having to see your code in a workbook. This also saves the system resources that would otherwise be required to display a workbook. Finally, the add-in is read-only so that users cannot make inadvertent changes to your code.