How can i assign values to the listbox in module pool

Hi

      i used pov event  and vrm_set_values to populate the values to the list box and but in selection field i can not get the values, please help me,

*&---------------------------------------------------------------------*

*&      Module  VRM_VBELN  INPUT

*&---------------------------------------------------------------------*

*       text

*----------------------------------------------------------------------*

MODULE VRM_VBELN INPUT.

select vbeln from vbak intotable t_vbeln upto500rows.

loopat t_vbeln.

move t_vbeln-vbeln to w_val-key.

append w_val to vrm_val.

clear w_val.

endloop.

CALLFUNCTION'VRM_SET_VALUES'

   EXPORTING

     ID                    = 'G_VBELN'

     VALUES                = vrm_val

* EXCEPTIONS

*   ID_ILLEGAL_NAME       = 1

*   OTHERS                = 2

           .

IF SY-SUBRC <> 0.

* Implement suitable error handling here

ENDIF.

ENDMODULE.

Thanks&Regards

Koteswara Rao.