這個BAPI有些字段沒有，可以用下面方法增強
1、se11創建結構，必須包含行項目號POSNR字段，和其他需要擴展的字段，如記賬碼Posting
Key、原因代碼Reason Code
2、SE19實現BADI增強ACC_DOCUMENT，這個增強是用來將BAPI_ACC_DOCUMENT_POST參數表EXTENSION2傳入系統表
3、使用BAPI_ACC_DOCUMENT_POST參數表EXTENSION2，將擴展字段傳入
詳細步驟如下：
1、創建結構，se11，很簡單，不再贅述，如下圖：
2、SE19實現BADI增強ACC_DOCUMENT
通過ACC_DOCUMENT help文檔知道，方法CHANGE用來完成字段的擴展，還有一個需要注意的是參考業務類型，這個一定要選對，不然執行BAPI的時候不會調用這個BADI，我用的是BKPFF，如下圖：
激活這個BADI實現。
雙擊change方法創建，可以查看ACC_DOCUMENT的實現例子CL_EXM_IM_ACC_DOCUMENT（R/3 4.7版本，其他版本可能名稱不一樣），，將這個實例的change方法的代碼直接copy過來，激活方法，代碼如下
***********************************************************************
* Example to move fields from BAPI parameter EXTENSION2 to structure *
* ACCIT (accounting document line items). *
* The dictionary structure (content for EXTENSION2-STRUCTURE) must *
* contain field POSNR, (TYPE POSNR_ACC) to indentify the correct line *
* item of the internal table ACCIT. *
***********************************************************************
DATA: wa_extension TYPE bapiparex,
ext_value(960) TYPE c,
wa_accit TYPE accit,
l_ref TYPE REF TO data.
FIELD-SYMBOLS: <l_struc> TYPE ANY,
<l_field> TYPE ANY.
SORT c_extension2 BY structure.
LOOP AT c_extension2 INTO wa_extension.
AT NEW structure.
CREATE DATA l_ref TYPE (wa_extension-structure).
ASSIGN l_ref->* TO <l_struc>.
ENDAT.
CONCATENATE wa_extension-valuepart1 wa_extension-valuepart2
wa_extension-valuepart3 wa_extension-valuepart4
INTO ext_value.
MOVE ext_value TO <l_struc>.
ASSIGN COMPONENT 'POSNR' OF STRUCTURE <l_struc> TO <l_field>.
READ TABLE c_accit WITH KEY posnr = <l_field>
INTO wa_accit.
IF sy-subrc IS INITIAL.
MOVE-CORRESPONDING <l_struc> TO wa_accit.
MODIFY c_accit FROM wa_accit INDEX sy-tabix.
ENDIF.
ENDLOOP.
3、使用BAPI_ACC_DOCUMENT_POST參數表EXTENSION2，將擴展字段傳入
**********************************************************************
*INTERNAL TABLE DECLARATION
**********************************************************************
*&—-G/L ACCOUNT ITEM
DATA: ACCOUNTGL TYPE STANDARD TABLE OF BAPIACGL09.
*&—CURRENCY ITEMS
DATA: CURRENCY_AMOUNT TYPE STANDARD TABLE OF BAPIACCR09.
*&—-RETURN PARAMETER
DATA: RETURN TYPE STANDARD TABLE OF BAPIRET2 WITH HEADER LINE.
*&—-it_extension2 ITEMS
DATA: IT_EXTENSION2 TYPE STANDARD TABLE OF BAPIPAREX WITH HEADER LINE.
*&—WORKAREA FOR ZEXTEN
DATA: WA_ZEXTEN LIKE ZEXTEN. ”ZEXTEN就是剛纔SE11創建的那個結構
**********************************************************************
*賦值
**********************************************************************
*& EXTENSION2擴展字段增強部分
WA_ZEXTEN-POSNR = '0000000010'. "憑證行項目
WA_ZEXTEN-RSTGR = '171'. "憑證行項目原因代碼
IT_EXTENSION2-STRUCTURE = 'ZEXTEN'.
IT_EXTENSION2-VALUEPART1 = WA_ZEXTEN.
APPEND IT_EXTENSION2.
*其他參數表的字段賦值如下例
HEADER-HEADER_TXT = 'TEST HEADER'."憑證擡頭文本
HEADER-USERNAME = SY-UNAME. "用戶名
HEADER-COMP_CODE = '1000'."公司代碼
HEADER-DOC_DATE = '20090618'."憑證中的憑證日期
HEADER-PSTNG_DATE = '20090618'."憑證中的記帳日期
HEADER-DOC_TYPE = 'S1'."憑證類型
* HEADER-BUS_ACT = 'RFBU'."交易業務
WA_ACCOUNTGL-ITEMNO_ACC = '0000000010'. "會計憑證行項目編號
WA_ACCOUNTGL-GL_ACCOUNT = '1002010105'. "總分類帳帳目
* WA_ACCOUNTGL-ITEM_TEXT = .
WA_ACCOUNTGL-BUS_AREA = '8000'. "業務範圍
APPEND WA_ACCOUNTGL TO ACCOUNTGL.
CLEAR WA_ACCOUNTGL.
WA_ACCOUNTGL-ITEMNO_ACC = '0000000020'. "會計憑證行項目編號
WA_ACCOUNTGL-GL_ACCOUNT = '1301040000'. "總分類帳帳目
WA_ACCOUNTGL-BUS_AREA = '8000'. "業務範圍
*WA_ACCOUNTGL-ITEM_TEXT = .
*wa_accountgl-ACCT_TYPE = 'R'.
APPEND WA_ACCOUNTGL TO ACCOUNTGL.
CLEAR WA_ACCOUNTGL.
WA_CURRENCY_AMOUNT-ITEMNO_ACC = '0000000010'. "行項目編號
WA_CURRENCY_AMOUNT-AMT_DOCCUR = '500'. "金額
WA_CURRENCY_AMOUNT-CURRENCY = 'RMB'.
APPEND WA_CURRENCY_AMOUNT TO CURRENCY_AMOUNT.
CLEAR WA_CURRENCY_AMOUNT.
WA_CURRENCY_AMOUNT-ITEMNO_ACC = '0000000020'.
WA_CURRENCY_AMOUNT-AMT_DOCCUR = '-500'.
WA_CURRENCY_AMOUNT-CURRENCY = 'RMB'.
APPEND WA_CURRENCY_AMOUNT TO CURRENCY_AMOUNT.
CLEAR WA_CURRENCY_AMOUNT.
*執行BAPI
CALL FUNCTION 'BAPI_ACC_DOCUMENT_POST'
EXPORTING
DOCUMENTHEADER = HEADER
*CUSTOMERCPD =
*CONTRACTHEADER =
*IMPORTING
*OBJ_TYPE =
*OBJ_KEY =
*OBJ_SYS =
TABLES
ACCOUNTGL = ACCOUNTGL
*ACCOUNTRECEIVABLE =
*ACCOUNTPAYABLE =
*ACCOUNTTAX =
CURRENCYAMOUNT = CURRENCY_AMOUNT
*CRITERIA =
*VALUEFIELD =
*EXTENSION1 =
RETURN = RETURN
*PAYMENTCARD =
*CONTRACTITEM =
EXTENSION2 = IT_EXTENSION2
*REALESTATE =
.
IF RETURN-TYPE NA 'EA'.
CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'
EXPORTING
WAIT = 'X'.
ENDIF.
如果還需要擴展其他字段，在結構ZEXTEN加入，然後在調用BAPI前對相應字段賦值，就行了。
