Given what you've said so far, it seems to me you're trying to use mailmerge for something it really isn't suited to. Mailmerges are for generating multiple copies of like documents, based on the known structure of a known data source and for which the mailmerge fields are essentially constant. Your requirement seems to necessitate the compilation of a single copy of a document from an unknown data source having an unknown structure and for which the end user is going to have to provide the names of in excess of 50 mergefields at runtime.

And this is supposed to be less error-prone than simply having someone fill out the data manually? Somehow I don't think so. Indeed, your client is making it so hard for someone who isn't a data & mailmerge specialist that they'll more than likely toss it in the too-hard basket. What is more, you'll end up to trying to push this lump of jelly up a wall with a programmer's toothpick, so to speak. All I can say is: good luck with the legal issues - you've go far weightier issues to deal with than the mere risk of "altering the table that is used to line up the fields with the form image".

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]