There is a design
pattern called Observer. It is useful to notify several objects (Observer) when something has happened to one instance (Observable).
It is commonly used in Ajax to notify several objects when an event (like onclick) occurs.
What you basically do is :
1. Have an Observable class
2. Have a few Observer classes
3. Register the Observers to the Observable object (addObserver)
4. Call notifyObserver when you want to notify all the observers that something has happened