Advise for Prepayment Available pop-up Note when clicking Invoice Validation.

Request: At the AP Invoice Workbench - Actions - Validation: We want to have the Prepayment Avaiable Note message pop-up when clicking Validation checkbox. Any suggestion or advise for how to achieve this, customized trigger, or personalization?

Currently: The below Note will pop-up while AP entering supplier name which has open prepayment. After clicking OK button, AP would continue entering the invoice and match receipts, etc…. But if there’re many items need to be matched under this invoice, it’s easy to forget apply prepayment after completing the whole invoice, which might be caused double pay to supplier.

Thanks!