How can I Import an AP invoice with two lines one wit withholdig tax and another without it?

Dear all,

     I'm triying to import an AP invoice with two lines one line have 21% tax and 15% withholding and the other one have 0% tax and doesn't have withholding.

Item Line 1 : 100 amount + 21 (21%) tax - 15 (15%) withholding tax

Item Line 2:  100 amount + 0 (0%) tax

When we create the interface invoice, on line 1 we put AP_INVOICE_LINES_INTERFACE.AWT_GROUP_ID = 10050 and on line 2  we put AP_INVOICE_LINES_INTERFACE.AWT_GROUP_ID = null. But wen we import the invoice we get the two lines with the 15% withholding tax. So we need manualy delete the withholdig tax on the second item line.

Is there any way that the AP open import interface doesn't put the withholdig tax on the second line??