You can use group option with CreateWindow, test this code if you have time :) , click somewhere on the big window and you can see the diffrents.
SuperStrict Local Style:Int = WINDOW_TITLEBAR|WINDOW_RESIZABLE|WINDOW_MENU|WINDOW_STATUS Local MainWindow:TGadget=CreateWindow("Parent",200,200,800,600,Null,Style) Local ChildWindow:TGadget=CreateWindow("Child",200,200,150,150,MainWindow,Style) Local NotChild:TGadget=CreateWindow("Not Child",300,300,150,150,Null,Style) Repeat WaitEvent() Select EventID() Case EVENT_WINDOWCLOSE End End Select Until KeyHit(KEY_ESCAPE)