The primary reason I write modular code is that it is self-documenting, easy to understand, and easy to maintain. A secondary reason is the ease of reuse.
One of the comments to my post Two new range functions: Union and Subtract (www.dailydoseofexcel.com/archives/2007/08/17/two-new-range-functions-union-and-subtract/) was a request for code to copy a range from one worksheet to another with certain ranges excluded. While I agree with DK that there’s no need to get fancy with something that is used once a month, I couldn’t pass up the opportunity to illustrate the ease of reuse of modular code.
For a version in a page by itself (i.e., not in a scrollable iframe as below) visit http://www.tushar-mehta.com/publish_train/xl_vba_cases/1102%20Modular%20code%20-%20ease%20of%20reuse.shtml