Professional Excel Development [Electronic resources] : The Definitive Guide to Developing Applications Using Microsoft® Excel and VBA® نسخه متنی

General Add-ins

General add-ins, also known as utility add-ins, are designed to enhance Excel by extending its feature set or providing connections between it and other programs. All Excel utility add-ins fall into this category, including most of the add-ins you will find in the Tools folder of the CD that accompanies this book. Like function library add-ins, general add-ins are designed to work with any arbitrary workbook the user opens. General add-ins are typically contained within a single .xla workbook, although larger examples may be distributed across multiple files. General add-ins are typically placed in the add-ins list of the Excel Add-ins dialog so the user can easily load and unload them as the need arises. They are provided with a friendly name and description in exactly the same way as described for a function library add-in in the previous section.Chapter 7 Using Class Modules to Create Objects.

The individual entry-point procedures of your add-in must also verify that the current state of Excel is valid for them to run. For example, if a procedure is designed to operate on a chart, but there is no chart currently active, your procedure must detect this and provide the user with an explanatory error message rather than falling over with a runtime error caused by an attempt to reference a nonexistent chart.