Extended Class Validation - Padding Key Value

[bbssupport]

I'm looking at using the extended class validation feature define some data classes for use in a grid.

Lets say i create a class for 'Customer Code' which links to the customer file in the extended validation feature to verify the customer code is valid. I'm facing an issue with being able to specify that the value entered should be padded with spaces up to the maximum field length before checking the customer file (eg user enters 'CASH' but the key on the customer file is 'CASH  ' because all customer codes are padded to 6 characters.

Is there a way that I can't see to achieve this?