FB01 uploading problem with posting keys

Question

Hi Gurus!
I created this program to upload the FB01 transaction froma  csv file using 'BAPI_ACC_DOCUMENT_CHECK'.
Everything seems to be working fine except for the fact that even when my csv file has the posting key of 31 for the  vendor and 40 for the gl it picks up 21 and 50 from somewhere and posts that which is wrong. I am not sure why this is happening and where its picking up the posting keys from inspite of the file indicating 31 and 40 respectively.
My file is as follows:
02232010;KR;2000;02222010;;CAD;154085;009571;31;925049;20706.84;V005;02222010;C;213728;40;3998;20706.84;1;EA;002;730019;730019 and as you see the 31 and 40 are mentioned in the file but after i run teh program and see the FB03 for the postings it shows me as follows.
2000     1     000001     21     2000     Trade Accts Payable                    6,935.41     CAD               730019               
2000     2     000002     50     3998     Trade AR Conversion                    6,935.41-     CAD          730019     730019     
Could anyone please tell me why is it picking up other posting key istead of mine being provided in the file.
Thanks

Answer 1

I followed this:
***Vendor account check***
    CLEAR wa_ap.
    wa_ap-itemno_acc         = 1.                           "Item No
    wa_ap-vendor_no         = tw_upload-newko.              "Vendor account no
    wa_ap-item_text         = tw_upload-sgtxt.
    APPEND wa_ap TO ta_ap.
***General Ledger account check***
    CLEAR wa_gl.
    wa_gl-itemno_acc         = 2.                           "Item No
    wa_gl-gl_account         = tw_upload-newko_2.           "General ledger account
    wa_gl-item_text          = tw_upload-sgtxt_2.
*    wa_gl-fis_period         = tw_upload-monat.
    wa_gl-pstng_date         = wa_header-pstng_date.
    wa_gl-costcenter         = tw_upload-kostl.             "Cost center
    wa_gl-profit_ctr         = tw_upload-prctr.             "Profit center
    APPEND wa_gl TO ta_gl.
***Currency check***
    CLEAR wa_curr.
    wa_curr-itemno_acc       = 1.
    wa_curr-currency         = tw_upload-waers.
    wa_curr-amt_doccur       = tw_upload-wrbtr .
    APPEND wa_curr TO ta_curr.
    CLEAR wa_curr.
    wa_curr-itemno_acc       = 2.
    wa_curr-currency         = tw_upload-waers.
    wa_curr-amt_doccur       = tw_upload-wrbtr_2 * -1 .
    APPEND wa_curr TO ta_curr.
**Bapi check for the record to post
    CALL FUNCTION 'BAPI_ACC_DOCUMENT_CHECK'
      EXPORTING
        documentheader = wa_header
      TABLES
        accountgl      = ta_gl
        currencyamount = ta_curr
        return         = ta_return
        accountpayable = ta_ap. " If return contains no errors then post documents