Hi I've been trying to create custom validation using exactly the instructions on the following page (yes, the VIN numbers works just fine for my purposes).
http://www.gravityhelp.com/documentation/page/Using_the_Gravity_Forms_%22gform_valiation%22_Hook
I inserted the cut and paste php referencing the form id number but the filter doesn't seem to be working. Am I missing something here in terms of the set up of the form itself? I added a custom field and gave it a new custom field name "validate-vin" and added in a CSS class using the same "validate-vin."