QUESTION: how to validate credit card number before sent to Versi gn?

We collect credit card info. on our site and send it to Verisign for processing. We collect the credit card info. on the last page of our registration form. We have about 50% of the credit card numbers declined because people use dashes in their cc number (even though our directions ask them not to). Is there anyway to incorporate the following function so that the dashes would be stripped out before going directly to Verisign for processing? or do I need to create a middle page that would validate the credit card info. before going to Verisign? If the latter is true, then is there a way I can run this validation "invisibly" - maybe using header(Location:....)? <? function clean_no($cc_no) { // Remove non-numeric characters from $cc_no return ereg_replace ('[^0-9]+', '', $cc_no); } ?> Thanks for your help, Shawna