standard invoice is not validated yet, but can be applied to prepayment invoice

The standard invoice is not validated yet, as it was matched to a PO but the PO had been cancelled and closed.

currently, my system allows it to be applied to a prepayment invoice, that will be an issue as the invoice can never be validated because the PO got cancelled and closed.

how can I forbid this kind of situation happens? I need forbid an non-validated invoice to be applied to a prepayment invoices or to be paid with normal payment process.

thanks

Jimmy