Paint Polygons or show infowindows on GoogleMaps

I want paint some things (Polygon, Infowindows) on GoogleMaps via JavaScript.
That works fine if I call the JavaScript by the MapClick event.
If I do this in the load method from the UserControl I ran into an error message “google not defined”.
How can I do this without automated at runtime without MapClick?

One idea is a timer, that works, but that was not an elegant solution I think…

Thanks
Dirk