SELECT-OPTIONS on Dialog programming screen

source: http://wiki.sdn.sap.com/wiki/display/ABAP/SELECT-OPTIONS+on+Dialog+programming+screen

TRICK: Define Selection-screen as subscreen and call that subscreen in the flow logic of the Screen.

Steps to get SELECT-OPTIONS in module pool programs.

Start one dialog program with SAPMZ_TEST.
Place the below code in the TOP include of the dialog program.
TABLES mara.
SELECTION-SCREEN BEGIN OF SCREEN 2100 AS SUBSCREEN.
SELECT-OPTIONS: matnr FOR mara-matnr.
SELECTION-SCREEN END OF SCREEN 2100. 
Create one screen 2000.
Go to Layout of the screen and Define subscreen area on the screen and Name it as g_subscreen.
Place the below code in the Flow logic of the screen.
PROCESS BEFORE OUTPUT.
  CALL SUBSCREEN g_subscreen INCLUDING 'SAPMZ_TEST' '2100'.

PROCESS AFTER INPUT.
  CALL SUBSCREEN g_subscreen.
Activate all.
Create Transaction code for the dialog program SAPMZ_TEST.
Execute the transaction code. You will see the select-option for matnr how we see on Selection-screen.