Thanks, this works marvelously. Using a combination of alt+f9, update all the file name strings, and ctrl+a > f9 I can easily switch between each version.

One last question though, do you have any tips using relative paths to the files? When I first tried this method, I went with relative paths and it was working fine, but as I played around with it (i.e. adding more fields, using bookmarks ect.) it stopped working with relative paths. Now, unless I use the full path, I get a "Error! Not a valid filename" message. I am not sure what changed.

Have you experienced any difficulty with relative paths? And, are there any tips you can share?

EDIT:
I did a bit of research, and apparently, in word, includedtext uses the active directory when using relative paths, so relatives paths sometimes work sometimes don't.

I got around this issue using the filename field like so {includetext "{filename \p}/../mySource.docx" someBookmark}.
I found this to be the best solution from what I read.