Customer Exit Text Does Not Get Executed

Question

Dear all,
I have a text variable to display the last date of a month, named ZT_LASTDATE.
Subsequently, I write an ABAP code in CMOD as follows:
CASE I_VNAM.
  WHEN 'ZT_LASTDATE'.
*    IF I_STEP = 2.
* Assign 0P_PER3 (Posting Period) value to v_month.
      CLEAR loc_var_range.
      READ TABLE i_t_var_range INTO loc_var_range WITH KEY VNAM = '0P_PER3'.
* Logic to convert Period 13, 14, 15 & 16 to Period 12.
      IF loc_var_range-low GT '012'.
        v_month ='12'.
* For normal periods (Period 01 - Period 12).
      ELSE.
        v_month = loc_var_range-low+1(2).
      ENDIF.
* Assign 0P_FYEAR (Fiscal Year) value to v_year.
      CLEAR loc_var_range.
      READ TABLE i_t_var_range INTO loc_var_range WITH KEY VNAM = '0P_FYEAR'.
      v_year = loc_var_range-low.
* Assign first date of the month i.e. 01 to v_date.
      v_date = '01'.
* Concatenate Year, Month & Date into ZW_DT1 as input
* for SLS_MISC_GET_LAST_DAY_OF_MONTH function module.
      CONCATENATE v_year v_month v_date INTO ZW_DT1.
* Call function module to get last date of the month.
* Input  : ZW_DT1 e.g. 20111201
* Output : ZW_DT2 e.g. 20111231
      CALL FUNCTION 'SLS_MISC_GET_LAST_DAY_OF_MONTH'
        EXPORTING
          day_in            = ZW_DT1
        IMPORTING
          last_day_of_month = ZW_DT2.
* Prepare last date of the month in DD.MM.YYYY format.
* ZW_DT2 date format        = 20111231
* l_s_range-low date format = 31.12.2011
      CLEAR l_s_range.
      l_s_range-low+0(2) = ZW_DT2+6(2).
      l_s_range-low+2(1) = '.'.
      l_s_range-low+3(2) = ZW_DT2+4(2).
      l_s_range-low+5(1) ='.'.
      l_s_range-low+6(4) = ZW_DT2+0(4).
      l_s_range-sign     = 'I'.
      l_s_range-opt      = 'EQ'.
* Send last date of the month output to ZT_LASTDATE variable.
      APPEND l_s_range TO e_t_range.
*    ENDIF.
ENDCASE.
However, when I execute my query, the variable text is displayed as &ZT_LASTDATE& and not as expected e.g. 31.12.2010.
I tried to debug it and found out that after the program stop at  
WHEN 'ZT_LASTDATE'.
it went straight to ENDFUNCTION of INCLUDE ZXRSRU01.
May I know what went wrong here?
Thanks!

Answer 1

Hi,
Uncomment the line I_STEP = 2 and then try debugging your code, put external break point on read table statement and keep on debugging. Don't put session breakpoint, for debugging you will have to use external break point. 
Regards,
Durgesh.