From libertybasic.conforums.com by Brent Thorn:

This little program demonstrates two concepts.

1. The CascadePosition sub gives your program the ability to open multiple windows arranged in the classic cascaded arrangement. CascadePosition must be called before a window is opened.

2. The TrapCloseCommon$() function and CommonClose sub provide a simple means of multiple window management by maintaining a count of the number of instances of open windows. To use these procedures, you must place the declaration for g.WindowCount near the top of your program and instead of doing a #handle "TrapClose etc" you must use #handle TrapCloseCommon$().

'* Cascading windows and instance counting
'* By Brent D. Thorn (http://www.b6sw.com/)
'* PUBLIC DOMAIN
 
Global g.WindowCount
 
Call CascadePosition
Open "1" For Window As #1
#1 TrapCloseCommon$()
 
Call CascadePosition
Open "2" For Window As #2
#2 TrapCloseCommon$()
 
Call CascadePosition
Open "3" For Window As #3
#3 TrapCloseCommon$()
 
Wait
 
Sub CommonClose handle$
Close #handle$
g.WindowCount = g.WindowCount - 1
 
Print "Closed ";handle$;". ";g.WindowCount;" window(s) open."
 
If g.WindowCount = 0 Then
Print "End of program."
 
End
End If
End Sub
 
Function TrapCloseCommon$()
TrapCloseCommon$ = "TrapClose CommonClose"
g.WindowCount = g.WindowCount + 1
End Function
 
Sub CascadePosition
offset = 0
 
CallDLL #user32, "GetSystemMetrics", _
_SM_CYCAPTION As ULong, _
cy As Long
offset = offset + cy
 
CallDLL #user32, "GetSystemMetrics", _
_SM_CYSIZEFRAME As ULong, _
cy As Long
offset = offset + cy
 
UpperLeftX = UpperLeftX + offset
UpperLeftY = UpperLeftY + offset
 
If UpperLeftX + WindowWidth > DisplayWidth _
Or UpperLeftY + WindowHeight > DisplayHeight Then
UpperLeftX = 1
UpperLeftY = 1
End If
End Sub