creating a varible with a customer exit

I need to pass a date back to a quyer which will be used in the selection criteria as the FROM date. I've attached the code below. When i run the query it doens't fill the FROM date on the screen with the right date. I am not sure what is wrong

CASE I_VNAM.

WHEN 'ZD_FROMDATE'.

IF i_step = 2.

READ TABLE I_T_VAR_RANGE INTO Loc_Var_Range

WITH KEY vnam = '0P_CSDAT'.

Clear L_S_Range.

CONCATENATE loc_var_range-low0(4) loc_var_range-low4(2) '01' INTO IMP_DATE_BEG.

APPEND L_S_Range TO E_T_RANGE.

ENDIF.

endcase.