formatting a Word document (with mail merge)

I have a Word document that is being used for a mail merge to generate letters to clients.
The main document contains some conditional merge conditions so it can be one or two pages in length.  And in some cases, another conditional merge condition, a third page with signature blocks is needed.  What I'm trying to figure out is how to configure a footer for the last page of the main document, which will never display on the signature page (if it exists) and will only display on the last page of the main portion of the document.
I assume this involves use of multiple sections but really don't have a clue how to accomplish it.

Thanks in advance.