Hey Dave.... is there a chance we can get this added into the code for credit card validation? If CreditCard is chosen for payment type, pass the CC# through this for validation....

private static bool IsValidNumber(string number)
{
    int[] DELTAS = new int[] { 0, 1, 2, 3, 4, -4, -3, -2, -1, 0 };
    int checksum = 0;
    char[] chars = number.ToCharArray();
    for (int i = chars.Length - 1; i > -1; i--)
    {
       int j = ((int)chars[i]) - 48;
       checksum += j;
       if (((i - chars.Length) % 2) == 0)
           checksum += DELTAS[j];
    }

    return ((checksum % 10) == 0);
} 

.... additionally, is there a quick and simple way to validate the MMYY to make sure that it is not in the past? These two things would have to be done with code-behind, because the usage of the text fields dynamically changes for the payment type... so, it's a Credit Card Number when Credit Card is selected, but a PO Number when Purchase Order is checked, so I can't do any of this as a regex, javascript, etc. It would have to be done conditionally as code-behind.