REPORT Z.
  data: w_auart like vbak-auart,  "current SalesDoc type
        w_auara like tvak-auara,  "Subsequent SalesDoc type
        w_vbak  like vbak.

  parameter p_vbeln like vbak-vbeln.

at selection-screen on p_vbeln.
  SELECT SINGLE auart FROM vbak into w_auart
    WHERE vbeln = p_vbeln.
  if sy-subrc <> 0.
    message e398(00) with 'Sales Doc' p_vbeln 'not found'.
  endif.

start-of-selection.
  SELECT SINGLE auara FROM tvak into w_auara
    WHERE auart = w_auart.
  if sy-subrc <> 0 or w_auara is initial.
    message e398(00) with 'Subsequent type not defined for' w_auart.
  else.
*   1. copy
    CALL FUNCTION 'SD_SALES_DOCUMENT_COPY'
         EXPORTING
              i_auarn       = w_auara
              i_vbeln       = p_vbeln.
*   2. paste
    CALL FUNCTION 'SD_SALES_DOCUMENT_SAVE'
         IMPORTING
              evbak         = w_vbak.
*   3. commit
    COMMIT WORK.
*   4. report
    write: / 'Sales Doc', w_vbak-vbeln, 'created.'.
  endif.