Closing a window when opening another!

Im still a bit new at this, but try Freegadget window1 after your button click but before you create the 2nd window. I chucked this together using GUI maker...

Global Win1
Global Win2
Global Button1 ;open window 2 from within window 1
Global Button2 ;open window 1 from within window 2
Global Button3 ;common exit button. 
CreateWin1()


While WaitEvent()<>$803

If EventSource() = Button1 Then
createWin2()
FreeGadget Win1
End If 

If EventSource() = Button3 Then
createWin1()
FreeGadget Win2
End If

If EventSource() = Button2 Then End


Wend


Function CreateWin1()
Win1 = CreateWindow("Window1",0,0,674,528,Desktop(),3)
Button1 = CreateButton("Open Window2",373,241,100,20,Win1,0)
SetGadgetLayout Button1,1,0,1,0
createexitbutton(Win1)
End Function


Function CreateWin2()
Win2 = CreateWindow("Window2",54,127,674,528,Desktop(),3)
Button3 = CreateButton("Open Window1",373,241,100,20,Win2,0)
SetGadgetLayout Button3,1,0,1,0
createexitbutton(Win2)
End Function


Function createexitbutton(window)
Button2 = CreateButton("Exit",178,240,100,20,window,0)
SetGadgetLayout Button2,1,0,1,0
End Function