Add-ins enable you to extend the capabilities of Office applications by adding custom commands and specialized features that meet a specific business requirement. Over time, the term "add-in" has been used to cover a wide range of different technologies, as described in Table 5-1.
Table 5-1. Add-In Types
VBA add-ins (Excel XLAs, Word DOTs)
Office applications support VBA add-ins that you can create with the VBA Editor included in each application.
Easy to develop.
Not compiled, run slowly, are susceptible to user corruption, lead to unstructured, unmaintainable code, and can pose a security risk.
Excel XLLs, Word WLLs, and Visio VSLs
Compiled, application-specific DLLs, developed in languages ...