page setup problem

I have a two page document with mail merge fields. It merges onto a
preprinted double sided form where page 1 is landscape and page 2 is portrait.

There is a greeting field at the top of page 2, but it prints on top of the
preprinted text. I tried reducing the top page margin but when I did this
the document becomes 3 pages according to the information bar. So the field
is in the correct place but the merge doesn't print double sided.

I've done a temporary fix by putting the field in a text box, but how do I
change the page margins so the document stays as 2 pages?

The office I'm in is using Word 97.

Thanks for any help.