How to change order of columns in wdp alv table

Hi Experts,

     Can anybody tell me how to change the order of columns in webdynpro alv table ,i have tried following code ,but this hav'nt worked,Please

let me know is there any other way ........advance thanks

CALLMETHODlo_value->if_salv_wd_column_settings~get_columns

    RECEIVING

      value = lt_columns.

* Get reference to each column and set the column position

  LOOPATlt_columns INTOls_column.

    lo_column = ls_column-r_column.

    CASEls_column-id.

      WHEN'VBELN'.

        lo_column->set_position('1').

      WHEN'MATKL'.

        lo_column->set_position('2').

      WHEN'POSNR'.

        lo_column->set_position('3').

      WHEN'MATNR'.

        lo_column->set_position('4').

    ENDCASE.

  ENDLOOP.

ENDMETHOD.

Regards

Sandesh