Hi John,

In the mail merge main document, use Alt+F9 to toggle on the field codes and
add the following formatting switch inside the closing }

\# ",$#.00"

Please post any further questions or followup to the newsgroups for the
benefit of others who may be interested.  Unsolicited questions forwarded
directly to me will only be answered on a paid consulting basis.

Hope this helps
Doug Robbins - Word MVP