Comparing subdocuments for differences

[Gajdar]

I've got some mass mailing software that I'm adding review capability to. The
basic methodology is the user picks a list of contacts and a mail merge
template and the software generates a Word document with each letter on a
separate page. The user can then edit and save. What I do internally is break
out each of the subdocuments and save them as separate documents. That works
fine.

Now I'm being asked for a review capability, which allows the user to
reconstruct the mass mailing and look at it. I've got that pretty much
working.

What I'm having trouble with is, if Word tells me that something in the
concatenated document has changed when the user saves or closes Word,
figuring out which subdocument has been edited. Document.Compare looks like
it would work if it returned a boolean, not a decorated document. I've tried
various kinds of checksums, but they don't seem to work with the Select.Text
output. There must be someway of comparing the before and after documents
programmatically, but I'm not finding it. Any suggestions?

PS I'm writing this beast in C++, but that's another story.