Problem in using WS_DELIVERY_UPDATE(updating the deliveries)

Hi Gurus,

Iam facing problem  i updating the deliveries using the fm WS_DELIVERY_UPDATE..This is the code..

MOVE : lwa_mchb-matnr   TO lwa_vbpok-matnr,

                   lwa_mchb-charg   TO lwa_vbpok-charg,

                   lwa_mchb-lgort   TO lwa_vbpok-lgort,

                   lwa_mchb-clabs   TO lwa_vbpok-lfimg,

                   lv_gross_weight  TO lwa_vbpok-brgew,

                   lwa_mchb-clabs   TO lwa_vbpok-ntgew.

                   lwa_vbpok-SPE_INB_ITM_UPD = 'X'.

            APPEND lwa_vbpok TO lit_vbpok.    

          CLEAR : lwa_idetail,

                  lwa_vbpok,

                  lv_gross_weight.

        ENDLOOP.

• Fill the header data

        lwa_vbkok-vbeln_vl  = gwa_header-vbeln.

        lwa_vbkok-wadat_ist = sy-datum.

        lwa_vbkok-bolnr     = gwa_header-bolnr.

        lwa_vbkok-traid     = gwa_header-traid.

        lwa_vbkok-spe_inb_dlv = 'X'.

• Call the function module to update the delivery

        CALL FUNCTION 'WS_DELIVERY_UPDATE'

          EXPORTING

            vbkok_wa                 = lwa_vbkok

            synchron                 = lc_x

            no_messages_update       = space

            update_picking           = lc_x

            commit                   = lc_x

            delivery                 = gwa_header-vbeln

            nicht_sperren            = lc_x

            if_database_update       = '1'

            if_error_messages_send_0 = lc_x

          TABLES

            vbpok_tab          = lit_vbpok

            prot               = lit_prot.

            commit work.

I have to update the following item fields

1>BATCH

2>LGORT

3>NTGEW

4>LFIMG

5>BRGEW...

also two header fields..The header fields are updated successfully,but the item fields are not updated..Please tell me where iam wrong...what else needs to be passed..

Your help us highly appreciated..

Regards,

Raj