Try using Microsoft Visual SourceSafe, VFP has native support for this application and will allow you to share your source/projects. If you havn't got access to this product then their is a free version control system with all the same functionality called FreeVCS available from:-

http://www.freevcs.de/index.htm

You will not get integrated VFP support with this (there is a DLL that can be used to integrate functionality) but it comes with a complete IDE and COMPLETE source code.