BEx: User exit for key date

Hi experts

We need to calculate the key date of a query feeded by a variable on 0CALMONTH.

But the coding below doesn't fill up the keydate.

Any ideas?

The coding:

WHEN 'ZKEY_DATE_001'.

    DATA: range_low_key_001 type d,
          key_002 type c,
          key_003 type d.

    IF I_STEP = 2.
      LOOP AT i_t_var_range INTO loc_var_range WHERE VNAM = 'ZCALMONTH_EV_001'.
        clear l_s_range.
        key_002 = loc_var_range-low + 1.
        concatenate key_002  '01' into range_low_key_001.
        key_003 = range_low_key_001 - 1.

        l_s_range-low = key_003.
        l_s_range-sign = 'I'.
        l_s_range-opt = 'EQ'.
        APPEND l_s_range TO e_t_range.
      ENDLOOP.
    ENDIF.