Add the following formatting switch inside the closing } of the mergefield.
Use Alt+F9 to toggle the display of the field codes.

\# "###'-'##'-'####"

For example

{ MERGEFIELD SSN \# "###'-'##'-'####" }

--
Hope this helps.

Please reply to the newsgroup unless you wish to avail yourself of my
services on a paid consulting basis.

Doug Robbins - Word MVP

"Helen" wrote in message
...
Hi,

I have created a mail merge in Word from an Excel spreadsheet. The
spreadsheet contains social security numbers that are stored as numbers
999999999 but formatted as 999-99-9999. When doing the mail merge Word
will
display the SSN as 999999999, not as 999-99-9999. How can I fix this?

Thanks!!

Helen