Negative POS payments

Is there a way to block or limit the ability for negative amounts to be entered into the payment amount box when parents (or staff) are preparing (via ledger or check-in) to pay on their account?

Often it appears that balances come over pre-filled (if they are overpaid), or keystroke errors occur where the negative is left IN the transaction. This results in a "refund" or payment BACK to the parent on the account, and taking away Center revenue instead of collecting it.

We have had 3 such situations this week alone (which is highly unusual). Example attached.