If you have to adjust conditions for your purchase order line and if during the use of method if_purchase_order_item_mm~set_conditions in BADI ME_PROCESS_PO_CUST you receive an error MEPO151 "Data ...
... of Attachments article you can connect to GOS from class CL_PO_HEADER_HANDLE_MM which contains method GET_GOS_MANAGER. You can do it for example in PROCESS_ITEM method of ME_PROCESS_PO_CUST . You'll ...