Tax Witholding required for VAT and GST

I need to withhold to my supplier both VAT and GST (Mexican Law) for every invoice, i did manage to get tax witholding for one account (GST) working, and then i manually was adding VAT withhold, i ran to a video on youtube with gave me a clue on how to do it automaticallly using normal tax category and negative tax rates

I can solve it this way but since i want to keep the system working as designed i just want to know if anyone figured out a way to withold on two different tax accounts using ERPNEX tax witholding as it is build. If there is no way i will use the workaround i designed.


Luis Montanaro