How to setup user validation in tamplete

Hi,

We are in R12 and when user define validations in format  iby_pay_ece it seem doesn't work the way it should be.

For example  Clearing payment method  user want to validate bank account equal to 1234 which work fine, it will rejecte all the ACH payment but we also have check default bank account to 1234, it also get reject. That is not good.

Is there any other ways to do add user validation in PPR? in 11i  clearing is the payment method so when upgrade to R12 we still have invoices and vendor setup as clearing.

Or is there a ways to add user description or detail of the error? Because user only have drop down list from form and the value fiield are share to all the payment method?