DFF Field Validation ( PAN No)

Hi, I have a field in supplier and customer page for capturing permanent account number (PAN). The requirement is to built in validation for the same as to how the PAN should be entered.

The format is CCCCCNNNNC where C = character and N = Numeric

How do I fulfill this? I cannot use special Validation type in Value set as the same is not applicable to OA Framework. It works only in forms I am not using india localization.