Do you mean that you have numbers in Excel that are formatted with
commas, and that those commas do not appear in Word?
If so, use Alt-F9 in your Word mailmerge main document to display the
field codes, e.g. something like
{ MERGEFIELD mynumber }
and change that to have a numeric formatting switch such as
{ MERGEFIELD mynumber \#",0" }
(you can usually get rid of the switch "\*Mergeformat" if it is there.
NB, you only need one comma in the format switch to specify "insert a
thousands separator/millions separator etc. - you do not have to spell
it out by using
\#"0,000" or \#"0,000,000"
etc. But the formatting you specify will replace any formatting you
specify in Excel.
Peter Jamieson
http://tips.pjmsn.me.uk