Importing customer / loan returns template


I have a need to import customer returns into X3 ( both normal and loan returns). How is this done as the template I built only imports the header record and not the edtail record, despite detail records info being specified during the import ( this is the source sales delivery number, delivery line number, item info, lot or serial number info etc).
I guess this is due to the left hand side selection that occurs during the normal processing.
Any help / idea is welcome.