EnableExplicit

Define EventID
Define a

If OpenWindow(0,0,0,500,250,"Window",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
  TextGadget(1,10,10,100,20,"0",0)
  
  SetTimer_(WindowID(0),0,1000,0)
Repeat
EventID=WaitWindowEvent()
Select EventID
  Case #WM_TIMER
    a+1
    SetGadgetText(1,Str(a))
EndSelect
Until EventID = #PB_Event_CloseWindow
EndIf