ABAP Program: show and hide windows by request

REPORT ZIMRETTT.
**********************************************************
* This program is not very useful, but interesting.
* When started, it hides the screen, it is running in.
* After a preset time (60 second) it sends a popup window
* asking the user, if he wants it to be awaken. In case the
* user does not answer in 3 seconds, it removes the popup
* window and goes back to sleep.
* Create the following little program and associate it
* with transaction code ZITS:
*
*REPORT ZIMRETST.
*DATA: ANSWER, A(8).
*TABLES: INDX.
*CALL FUNCTION 'POPUP_TO_CONFIRM_STEP'
* EXPORTING
* DEFAULTOPTION = 'N'
* TEXTLINE1 = 'Do you want to awake the'
* TEXTLINE2 = ' sleeping window?'
* TITEL = 'You have 3 seconds to answer'
* CANCEL_DISPLAY = ' '
* IMPORTING
* ANSWER = ANSWER.
*IF ANSWER = 'J'.
* A = 'ZIZIZI'.
* EXPORT A TO SHARED BUFFER INDX(ST) ID 'ZAZAZA'.
*ENDIF.
**********************************************************
*
TABLES: INDX.
DATA: A(8) VALUE 'ZAZAZA'.
DATA: MODE LIKE SY-INDEX.
* Put my mark into the shared buffer
EXPORT A TO SHARED BUFFER INDX(ST) ID 'ZAZAZA'.
* Hide myself
CALL FUNCTION 'SAPGUI_SET_PROPERTY'
DESTINATION 'SAPGUI'
EXPORTING PROPERTY = 'VISIBLE'
VALUE = ' '.
* Wait for being called back
DO.
* Sleep for 60 seconds
CALL FUNCTION 'ENQUE_SLEEP'
EXPORTING
SECONDS = 60.
* Ask the user, if he wants me back
CALL FUNCTION 'TH_CREATE_MODE'
EXPORTING
TRANSAKTION = 'ZITS'
IMPORTING
MODE = MODE.
* Wait 3 seconds for the answer
CALL FUNCTION 'ENQUE_SLEEP'
EXPORTING
SECONDS = 3.
* Check if I am wanted back. If not: go back to sleep
IMPORT A FROM SHARED BUFFER INDX(ST) ID 'ZAZAZA'.
* Delete the popu window
CALL FUNCTION 'TH_DELETE_MODE'
EXPORTING
MODE = MODE.
* Exit if asked so
IF A = 'ZIZIZI'.EXIT.ENDIF.
ENDDO.
* No more sleep, redisplay myself
CALL FUNCTION 'SAPGUI_SET_PROPERTY'
DESTINATION 'SAPGUI'
EXPORTING PROPERTY = 'VISIBLE'
VALUE = 'X'.