Return order partner function line item wise different ???

Dear Expert,

If i created two invoices for same customer and with same material one invoice include sales employee and other invoice there is without sales employee

now if customer return two material which belongs to above two different invoices for that i will create single return order but in that return order one invoice belongs to sales employee and other without so in that return order i want the same

like in that return order if i check line item partner detail it should show if that line item belongs to sales employee then it should show sales employee and if that line item don't belongs to sales employee it should not show

Please guide