#CCHILDREN_TITLEBAR = 5

Structure TITLEBARINFO
  cbSize.l
  rcTitleBar.RECT
  rgstate.l[#CCHILDREN_TITLEBAR+1]
EndStructure

pti.TITLEBARINFO\cbSize = SizeOf(TITLEBARINFO)

If OpenWindow(0,0,0,500,250,"Window",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
  GetTitleBarInfo_(WindowID(0),pti)
  MessageRequester("","Höhe der Titelleiste: "+Str(pti\rcTitleBar\bottom-pti\rcTitleBar\top),0)
Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow
EndIf