Formatting problem with telephone numbers in excel.

I have a large excel file (905 names) where the telephone number is formatted xxx-xxx-xxxx.    The phonebank program I'm using will not accept numbers in this format - they need to be xxxxxxxxxx or (xxx)xxx-xxxx.

Can anyone tell me a quick way to change these numbers to either of the accepted formats.   The only way I know of is to retype them directly.

Thank you.