If OpenWindow(0,0,0,500,250,"Window",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
Repeat
EventID=WaitWindowEvent()
If GetAsyncKeyState_(#VK_A)
  MessageRequester("","Taste wurde gedrückt",0)
EndIf
Until EventID = #PB_Event_CloseWindow
EndIf