[Ace73]

Estimado
Supongo que ya realizo las ampliaciones de la estructuras de la BAPI agregando los campos Z. Despues de eso de debe ocupar en la BAPI la estructura EXTENSIONIN, esta extension sirve para varias BAPIs incluso la que quieres usar SD_SALESDOCUMENT_CREATE .

form LLENA_AMPLIACION tables p_extensionin STRUCTURE BAPIPAREX
using p_usermodifica
P_VBELN.

DATA: wa_extensionin TYPE bapiparex,
wa_bape_vbak TYPE bape_vbak,
wa_bape_vbakx TYPE bape_vbakx.

wa_bape_vbak-VBELN = P_VBELN.
wa_bape_vbakx-VBELN = 'X'.

wa_bape_vbak-ZZUSERMODIFICA = p_usermodifica.
wa_bape_vbakx-ZZUSERMODIFICA = 'X'.

wa_extensionin-structure = 'BAPE_VBAK'.
MOVE wa_bape_vbak TO wa_extensionin-valuepart1.
APPEND wa_extensionin to p_extensionin.
CLEAR wa_extensionin.
wa_extensionin-structure = 'BAPE_VBAKX'.
MOVE wa_bape_vbakx TO wa_extensionin-valuepart1.
APPEND wa_extensionin to p_extensionin.
endform. " LLENA_AMPLIACION

* y en la llamada a la funcion
*Se llena la estructura de ampliacion segun campos informados
DATA: extensionin LIKE STANDARD TABLE OF bapiparex WITH HEADER LINE.
REFRESH extensionin.
PERFORM llena_ampliacion TABLES extensionin
* USING header_in
USING I_USERMODIFICA
I_VBELN.

CALL FUNCTION 'BAPI_CUSTOMERQUOTATION_CHANGE'
EXPORTING
SALESDOCUMENT = I_VBELN
QUOTATION_HEADER_IN = IT_QUOTATION_HEADER_IN
QUOTATION_HEADER_INX = wa_QUOTATION_HEADER_INX
TABLES
RETURN = RETURN
QUOTATION_ITEM_IN = it_quotation_item_in
QUOTATION_TEXT = I_QUOTATION_TEXT
EXTENSIONIN = extensionin.

CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'
EXPORTING
WAIT = 'X' .


Espero te ayude porque a mi me funciona.

Saludos.