How to create a temporary purchase order

dear all：

           I want to create a temporary purchase order with  bapi  (  BAPI_PO_CREATE1 )

           I send parameters 

                                    POHEADER-MEMORY = 'X'.

                                   POHEADER-MEMORYTYPE = 'H'.

                                    POHEADERX-MEMORY = 'X'.

                                   POHEADERX-MEMORYTYPE = 'X'.

           But the result is not successful.

           Please give me some advice and methods, thank you very much！