Problem with 'AC_DOCUMENT_RECORD' FM ...Urgent Please !!!!!

i call the following code and i take always the same DOCNR in my itab.The number is the first result that FM give to me .At the next lines i take the same result ....

    
   DATA : BEGIN OF ITAB OCCURS 0,
        BUKRS       LIKE ANEK-BUKRS,
        ANLN1       LIKE ANEK-ANLN1,
        ANLN2       LIKE ANEK-ANLN2,
        BELNR       LIKE ANEK-BELNR,
        GJAHR       LIKE ANEK-GJAHR,
        AWTYP       LIKE ANEK-AWTYP,
        AWORG       LIKE ANEK-AWORG,
        AWSYS       LIKE ANEK-AWSYS,
        DOCNR       LIKE ACC_DOC-DOCNR,
        ICON2       LIKE ICONS-L4,
        CELLCOLOR TYPE LVC_T_SCOL,
        SEL,
        END OF ITAB.
*************END MY BASIC ITAB *********************
DATA : INS TYPE TABLE OF ACC_DOC WITH HEADER LINE. "LIKE ACC_DOC OCCURS 0 WITH HEADER LINE. 
......
......
.......


   CLEAR ANEK.
    SELECT * FROM ANEK WHERE BUKRS IN SBUKRS
                       AND   ANLN1 IN SANLN1
                       AND   ANLN2 IN SANLN2
                       AND   GJAHR IN SGJAHR.
                      

    IF SY-SUBRC = 0.
        MOVE-CORRESPONDING ANEK TO ITAB.
    ENDIF.

    CALL FUNCTION 'AC_DOCUMENT_RECORD'
      EXPORTING
        I_AWTYP            =  ANEK-AWTYP
        I_AWREF            =  ANEK-BELNR
        I_AWORG            =  ANEK-AWORG
        I_AWSYS            =  ANEK-AWSYS
        I_AWTYP_INCL       = 'BKPF'
        I_AWTYP_EXCL       = ' '
        I_BUKRS            = ANEK-BUKRS
        I_VALUTYP          = '0'
        X_DIALOG           = ' '
     TABLES
        T_DOCUMENTS        = INS
*     EXCEPTIONS
*       NO_REFERENCE       = 1
*       NO_DOCUMENT        = 2
*       OTHERS             = 3
              .
    IF SY-SUBRC <> 0.
* MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
*         WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
    ENDIF.

<b>    MOVE INS-DOCNR TO ITAB-DOCNR.    " i take the same result always !!!!</b>

    CLEAR INS-DOCNR.

    APPEND ITAB.
    ENDSELECT.

Points will be rewarded !!!!!

Please help ....