Selection OPTION: Date input problem in Module POOL through Subscreen

Question

Dear ALL,
Being new to ABAP, I am struck in a Problem.
Requirement:
I want an option on the Screen( My Screen 9000) for Date Range. Through this Date-Range I want to filter and pull some data from
Database.
As Date Range Selection option is possible only through Sub-Screen integration. Hence I integrated a Sub-Screen 400 (as below) and named the Sub-Screen area as SEL on my screen.
Problem: As soon as I enter the dates on the screen, then those dates are not taken up by the code.
During debugging I saw the the S_datum-low and S_datum-high are empty (in fact 00000000)
The code follows:
PROCESS BEFORE OUTPUT.
MODULE STATUS_9000.
  Call SUBSCREEN SEL  INCLUDING sy-repid '400'.
PROCESS AFTER INPUT.
  MODULE USER_COMMAND_9000.
DATA:  gv_datum     Type   dats,
SELECTION-SCREEN BEGIN OF SCREEN 400 AS SUBSCREEN.
    SELECT-OPTIONS: s_datum FOR gv_datum.
SELECTION-SCREEN END OF SCREEN 400 .
Plz help where I am missing something.
Regards
Chandan

Answer 1

Call the subscreen during the AT SELECTION-SCREEN event.
SELECTION-SCREEN BEGIN OF SCREEN 400 AS SUBSCREEN.
SELECT-OPTIONS: s_datum FOR gv_datum.
SELECTION-SCREEN END OF SCREEN 400 .
AT SELECTION-SCREEN.
   CALL SCREEN 100.
*&      Module  STATUS_0100  OUTPUT
*       text
MODULE status_0100 OUTPUT.
   SET PF-STATUS '0100'.
*  SET TITLEBAR 'xxx'.
ENDMODULE.                 " STATUS_0100  OUTPUT
*&      Module  USER_COMMAND_0100  INPUT
*       text
MODULE user_command_0100 INPUT.
   CASE sy-ucomm.
     WHEN 'BACK' OR 'EXIT' OR 'CANCEL'.
       LEAVE TO SCREEN 0.
   ENDCASE.
ENDMODULE.                 " USER_COMMAND_0100  INPUT