Update field ref_doc_ca in vbap

Hi all,

I want to change the value of the Document category of preceding SD document.

But it does not work...

order_headerx-updateflag = 'U'.

CLEAR: order_item, order_itemx.

REFRESH: order_item, order_itemx.

order_item-itm_number = it_vbap-posnr.

order_item-ref_doc_ca = 'A'.

APPEND order_item.

order_itemx-itm_number = it_vbap-posnr.

order_itemx-updateflag = 'U'.

order_itemx-ref_doc_ca = 'X'.

APPEND order_itemx.

• Change Quotes

CALL FUNCTION 'BAPI_SALESORDER_CHANGE'

EXPORTING

salesdocument = it_vbap-vbeln

order_header_inx = order_headerx

TABLES

return = return

order_item_in = order_item

order_item_inx = order_itemx.

APPEND LINES OF return TO return_all.

IF sy-subrc EQ 0.

CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'.

ENDIF.

Any ideas?

regards