Oxford, UK, Category Theory - a branch of mathematics has been used by a researcher Jocelyn Paine to set up a Web-based software library for Excel users.
It is very interesting to see the spreadsheet horror stories at this link that prompted Paine to create the robust modularized web based excel library.
Only time will tell how the experiment goes. It may be of value if each module comes up with clear documentation about who did it for what purpose and what errors have been rectified. May be a Wiki approach can help. Can this be a web service - just thinking aloud?
Anyway Paine has an (Dot) org site at http://www.spreadsheet-parts.org/
His before and after modularity cartoons also I liked. The quotes on why modularize are also of interest