You could use Validation. Assuming the data entry col. is
col. A, select col. A, go Data Validation,
choose "Custom", and in the "Formula" box put:

=AND(LEN($A1)=16,ISNUMBER(1*LEFT($A1,15)),ISNUMBER (1*RIGHT
($A1,15)))

But Validation is not bulletproof. A user can easily
override the Validation by copying/pasting or going
through the Edit Clear Clear All.

Format the column as "0000-0000-0000-0000".

HTH
Jason
Atlanta, GA


-----Original Message-----
I am trying to format a cell to a credit card format, so
the user can enter
only the numbers and have the dashes between each set of
four digits auto
populate. I have tried using both 0000-0000-0000-0000
and
####-####-####-####, and each of these puts a zero at
the end. Any
suggestions? THanks in advance for your help.
.