how to use BAPI_SALESORDER_CHANGE update ref.doc number ??

I try to update material number and update reference doc and  reference item.

However, VBAP-VGPOS does not updated. Please advise.

   CLEAR ORDER_ITEM_IN.

   ORDER_ITEM_IN-ITM_NUMBER    = '000010'.

   ORDER_ITEM_IN-MATERIAL         = 'ABC22222'   " ( change from ABC11111 to ABC22222 )

   ORDER_ITEM_IN-PLANT               = '1001'

   ORDER_ITEM_IN-TARGET_QTY    = '1'.

   ORDER_ITEM_IN-REF_DOC          = CONTRACT.       

   ORDER_ITEM_IN-REF_DOC_IT     = CONTRACT_ITM. ( " change from item 10 change to item 20 )

   ORDER_ITEM_IN-REF_DOC_CA   = 'G'.

   APPEND ORDER_ITEM_IN.

 

   CLEAR ORDER_ITEM_INX.

   ORDER_ITEM_INX-ITM_NUMBER   = '000010'.

   ORDER_ITEM_INX-UPDATEFLAG   = 'U'.

   ORDER_ITEM_INX-MATERIAL        = 'X'.

   ORDER_ITEM_INX-PLANT              = 'X'.

   ORDER_ITEM_INX-TARGET_QTY   = 'X'.

   ORDER_ITEM_INX-REF_DOC          = 'X'.

   ORDER_ITEM_INX-REF_DOC_IT     = 'X'.

   ORDER_ITEM_INX-REF_DOC_CA   = 'X'.

   APPEND ORDER_ITEM_INX.

 

 

CALL FUNCTION 'BAPI_SALESORDER_CHANGE'

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