The Handle property indicates the handle of the event, and it is unique while the event is living. The Handle value is automatically allocated by the control as soon as the event is being created. The AddEvent event occurs once a new event is created/added. The Start/End properties of the event specifies the margins of the event. The Handle property is read only, so the user can not change it. You can use the UserData property to associate any extra data to the event. The KnownProperty(exEventID) property specifies the event's identifier. The Handle is automatically generated by the control, and can not be changed, while the IDentifier can be set by the user.