Need to generate multiple COPA documents while settling Internal order

Here internal order created through CRM and internal order master data having material X it is instrument material and we performed some service through billing document and billing document having multiple line items each line item having different materials (A,B,C)internal order collecting the all revenue from billing document But while doing the Internal order settlement system it generate the one PA document and characteristics material filed updating with internal order master data material(instrument material) but my business want to expecting the multiple line items in PA document along with material field needs to update as per the billing document line item.

Can any one help me on this