You can document your (custom) events thrown by custom classes. It is easy. Just add event metatags as described in AS3 Event Metatags And Custom Events. Now you can document these events like this:

	 * Dispatched when item has been removed.
	 * @eventType
	[Event(name="removed", type="")]

	public class Actor extends EventDispatcher
		// throw event somewhere in here
		// ........

The documentation can be seen while adding the event listener to your instance (at least inside eclipse) or when you decide to generate ASDoc html files.