Voucher Build - Sales and Use Tax

We populate voucher staging tables with data from a third party.  They are PO vouchers.  Many times the SUT applicability is different from that in the purchase order and we want to use the information from the staging table, not the PO. 

Voucher build will use the value in the staging table if the voucher source is XLS, XML or EDI for the fields TAX_CD_VAT, MATCH_LINE_OPT, TAX_CD_SUT, VAT_TXN_TYPE_CD, VAT_USE_ID,  VAT_APPLICABILITY, VAT_TREATMENT if there is a value in the voucher line staging table.  However, it always gets the SUT_APPLICABILITY from the purchase order. We need to use the SUT_APPLICABILITY field from the staging table if it is populated.  Is there anyway to do this?