Try this:
mainwin=CreateWindow("main",200,200,400,300,0,3) helpwin=CreateWindow("help",150,80,100,80,0,3) ActivateGadget mainwin quit=False Repeat ev=WaitEvent() Select ev Case $803 If EventSource()=mainwin If helpwin<>0 FreeGadget helpwin FreeGadget mainwin quit=True EndIf If EventSource()=helpwin FreeGadget helpwin : helpwin=0 EndIf End Select Until quit=True End