Warning for selecting debit supplier in A/P Cash Transaction

We don't want to be able to tick a debit amount on our payables account in a Cash Transaction if it results in a net debit balance selected for payment, as it puts money into our bank account. This ends up creating extra work as it has to be reversed off our bank account and put back on to our payables. It would help if we had a pop up to remind us that we shouldn't do that.