The StartUpdateEvent/EndUpdateEvent methods record and add changes of the current calendar-event to the control's Undo/Redo queue. You can use the StartBlockUndoRedo / EndBlockUndoRedo methods to group multiple Undo/Redo operations into a single-block. The AllowUndoRedo property specifies whether the control supports undo/redo operations for objects (calendar-events). No entry is added to the Undo/Redo queue if no property is changed for the current calendar-event. Each call of the StartUpdateEvent must be succeeded by a EndUpdateEvent call. The UndoListAction property lists the Undo actions that can be performed in the chart. The RedoListAction property lists the Redo actions that can be performed in the chart.

The StartUpdateEvent/EndUpdateEvent methods can record changes for all properties from 1 ( exEventStartDateTime) to EXEVENTMAX listed by EventKnownPropertyEnum type.

The Undo/Redo records show as:

• "UpdateEvent;EVENTID", indicates that one or more properties of the calendar-event has been updated, using the StartUpdateEvent / EndUpdateEvent methods

within the UndoListAction/RedoListAction result