How to trigger a custom Warning Message in AP Invoice screen based on Outstanding Prepayments?

We have a specific business requirement in Oracle Fusion Payables (AP) and would like to know the best approach to achieve it.

Requirement:When a user creates and validates an AP invoice that is matched to a Purchase Order (PO), the system should display a Warning Message if there is an existing Prepayment invoice associated with the same PO that meets any of the following conditions:

• Unpaid (Payment status is not 'Fully Paid').
• Paid but not yet applied (Amount available for application is > 0).
• Partially applied (Remaining unapplied amount exists).

The goal is to alert the user to apply the outstanding advance before proceeding with the standard invoice payment.