ACCOUNT PAYABLE: Calculate VAT amount after deduct retention amount

Hi,

For ERP JD Edwards E1 TR 9.2.7.3.

How can we create a voucher when first needs to deduct a retention and the calculate VAT to the result amount?

Example:

Gross subcontractor costs            4,333.33

Less: retention    (5%)                        -216.67

Net subcontractor costs                 4,116.66

VAT on subcontractor voucher (20%)  823.33

Thanks,

Yhisleym Ruiz.