BAPI_SALESORDER_CHANGE. Error V1 045 -- Indicate number of document.

Question

Hi Experts.
When a pre-order (ZAG) it's confirmed in SAP, we make an oficial order (TA), then, when save the oficial order I need delete the field LCNUM in pre-order.
I'm using this BAPI, in a USER EXIT inside program SAPVM45A, when the number of document it's the pre-order.. but it failed, and return to me the message error that I don't indicate the number of document.
I find where it's the fail, when called to this function
  call function 'SD_SALES_DOCUMENT_READ'
there is a moment in the code with that
VBAK-VBELN = DOCUMENT_NUMBER.
  PERFORM BELEG_LESEN(SAPMV45A).
  PERFORM KONV_SELECT(SAPFV45P).
Well, when called the perform BELEG_LESEN, ---> VBAK-VBELN LOST , yes I tell you the true..., LOST the value of the pre-Order...
I think that when I call this function it's while save a order, program lost the value
Example of the code:
l_saledocument = v_vbelv. "Number of pre-po
          l_order_header_in-doc_num_fi = l_lcnum. "l_lcnum it's empty because I want update INITIAL in pre-po
          l_order_header_inx-doc_num_fi = 'X'.
          l_order_header_inx-updateflag = 'U'.
       Llamada a la bapi
          CALL FUNCTION 'BAPI_SALESORDER_CHANGE'
            EXPORTING
              salesdocument    = l_saledocument
              order_header_in  = l_order_header_in
              order_header_inx = l_order_header_inx
            TABLES
              return           = li_return.
          READ TABLE li_return WITH KEY type = 'E'.

Answer 1

Hi Pedro,
have a look to SAP Note 1232196.
You have to call FM SD_SALES_DOCUMENT_INIT before calling BAPI
Hope it helps
Lorenzo