Tagging WHT to suppliers

Hi All,

Sri Lankan tax regulations say that when we are paying a supplier, if the payment exceeds 50,000 per month or 500,000 per annum, we need to deduct 5% of the payment as Withholding Taxes. Presently what we do is we manually monitor the payments and as and when payments exceed these thresholds, we manually tag in the supplier screen

Suppliers > Entry : Call Supplier > Sites > Withholding Tax : Check 'Allow Withholding Tax'

Is there any way that we can automate this process in AP where as soon as the payments per month hit 50,000 or payments per year hit 500,000, the system will give us a warning or prevent us from making further payments till we tag 'Allow Withholding Tax'?