Clarion: Working ProgressBar in a TightLoop

ProgressInTightLoop.clw

  PROGRAM
! Purpose: to show that a progress bar can be updated in a tight loop
  MAP
  END

ProgressBar LONG
Window WINDOW('Test Progress Bar in Tight Loop'),AT(,,463,70),GRAY,FONT('Segoe UI',8),SYSTEM
		BUTTON('Start Tight Loop'),AT(191,39,,14),USE(?Start),DEFAULT
		PROGRESS,AT(13,13,400),USE(ProgressBar),RANGE(0,100)
	END
  CODE
  OPEN(Window)
  ACCEPT
	CASE ACCEPTED()
	  OF ?Start; DO TightLoop
   END
  END

TightLoop ROUTINE
	DATA
N    LONG
   CODE
   ProgressBar = 0
   ?ProgressBar{PROP:RangeHigh} = 10^5 

   LOOP N = 1 TO 10^8
     IF N % 1000 = 0
        ProgressBar += 1
        DISPLAY(?ProgressBar)
     END
   END

   MESSAGE('Done')

Hi, iam new in Clarion, Known that i wish if you can help me
what CODE MEANS IT , IN WHICH code belong

"CODE"
OPEN(Window)
ACCEPT
CASE ACCEPTED()
OF ?Start; DO TightLoop
END
END

thanks regards