An EventSink is the mechanism through which a client listens for events from an Automation server. Not all Automation interfaces expose events. The Automation wizard exposes the interface’s events when you set the Generate Event Support Code option. Event sets are defined as a dispinterface. This allows a container to implement, at compile time, a sink object whose IDispatch can handle any arbitrary dispinterface at run time. The container uses the object's type information to display a list of events to the user, allowing him to assign actions to those events. The sink maps a dispID event to some action to execute, so it does not need to know the semantics of the event itself. 

EventConnect