Customizing Third-Party Resources
In theory, any Excel resource can be tweaked or customized to meet your exact needs. In practice, however, customizing isn’t quite that easy. While many Excel resources are easy to modify, others range from difficult to just about impossible to modify. As a rule, worksheets are the easiest Excel resources to modify, followed by templates, custom functions, add-ins, and applications—in that order.
The language used to write the resource also plays a part in how easy it is to customize. Parts of the resource, especially custom functions and add-ins, often include modules written in VBA, C, or some other language.
Excel resources can also incorporate modules written in languages such as C, typically as add-ins or custom functions. Unless you’re familiar with the language being used, however, it’s very difficult to change or replace those parts of the resource.
Finally, there are legalities to consider. You may be prohibited by the terms of the licensing agreement from modifying part or all of the resource. In addition, some of the worksheets may be hidden or locked to keep anyone from modifying them. Sometimes this restriction is intended to protect curious users; sometimes it’s to protect the author’s intellectual property. While unhiding and unlocking Excel worksheets is not technically difficult, it may be a violation of copyright.