DFF Warning message

I have a DFF in classic page (Descriptive Flexfield) in Oracle Fusion Procurement that captures an amount from EPM. I would like to know if there is a way to enforce a validation rule on a Purchase Requisition (PR) so that the EPM Amount must match the Approval Amount.

My requirement is:

• If the EPM Amount is not equal to the Approval Amount, the system should display an error or validation message.
• The user should not be able to submit the requisition until the amounts match.
• The behavior should be similar to a mandatory field validation, where the transaction cannot proceed until the validation condition is met.