This seems to be working.
My Excel VBA application generates the mail merge documents (reports), saves and displays them. The user can then view the merged documents and edit. However, they are unable to save them after they make the edits. They receive an error : "Cannot Complete the Save Due To File Permission Error"

When this happens, the user has to close the document, and reopen it from it's saved location. Edit changes can then be saved. Are the mail merge documents being saved in a format that doesn't allow them to save after created?

Additionally, all the generated reports are in "Compatibility Mode". Not sure why.