If OpenWindow(0,0,0,500,250,"Window",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
  ComboBoxGadget(1,10,10,100,20,0)
  
  SendMessage_(GadgetID(1),#CB_SETDROPPEDWIDTH, 500,#Null)
Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow
EndIf