In Word, reveal the field codes using Alt-F9, so you see

{ MERGEFIELD total }

not <<Total>>, or a preview result. You must already have a "Total"
MERGEFIELD in your mail merge main document to display the content of your
TOTAL column.

After the word "total" but before the closing field brace, type a space,
then \#"$,0.00"

Then use Alt-F9 again to toggle the fields off, and either preview a
different record or attempt the merge. Make sure the double quotes are
straight quotes, not curly quotes. The amount should be formatted more or
less as you wanted. If it is not, something else must be wrong, and please
tell us what you see.

--
Peter Jamieson
MS Word MVP

Hi Ian,

Press Alt+F9 to toggle on/off the field codes

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