Unlocking and re-locking the document for forms in VB did the trick.

As for other kind suggestions:

I have no interest in introducing a 3rd-party tool into my company's increasingly paranoid (with some justification) IT security environment.

Using a linked document property field hadn't occurred to me, and I will keep this in mind for future projects. For now, this one is already done.

I realize that the document protection offered by Word is not really secure, but it is good enough for my current purposes. If the stakeholders in this document want better security, I'll cross that bridge when I get to it.

Thanks to all for their input.