And I'm begining to wish I didn't :-) Even if by some miracle I find a way to allow the user to edit this document, there is only a 50/50 chance it will work in earlier versions.

Well, this is the problem with implementing interfaces in VFP - Microsoft keeps changing them in each version. So, if you do not know which version is going to be on the client machine, you need to create separate handler classes for each version, and test to see which version of Word is installed on the end-user's machine so that you instantiate the correct version of your event handling object.

I am doing this same sort of thing in C# right now and nice thing about the Visual Studio Tools for Office is that I can just add a reference to Microsoft.Office.Interop.Word for Office 2007 and it will work no matter which version of Word is installed because it is backward compatible.