Check out the quickstart...

http://www.gotdotnet.com/quickstart/aspplus/doc/webvalidation.aspx

This doesn't have exactly what you need, but I think it would get you 
started on your own custom validator or regex validator.

> I need to code up the Luhn Mod 10 system or something similar to do 
> credit card number validation before it is sent off to the server.  I 
> have some code but it is coded for VB and I need it to work with C# any 
> information and/or help woudl be greatly appreciated..
> 
> Morgan