Excel's maximum precision is 15 digits. So to handle 16 digits, you need to
use text, not numbers. Therefore formatting will not help you.

You can format with a formula something like this:
=if(however you tell Visa vs Amex,left(a1,4)&" - "&mid(a1,5,4)&" -
"&mid(a1,9,4)&" - "&right(a1,4),left(a1,4)&"-"&mid(a1,5,6)&"-"&right(a1,5))

Regards,
Fred

"smartgal" wrote in message
...
I have a cell in which the user will input a credit card number and I want
it
to display a format based on the type of card. So Visa / MC should be
"####
- #### - #### - ####" but Amex should be "####-######-#####" - the user
will
choose the type of card in another cell so what's the most effective way
to
conditionally format the input to display properly based on the card type?