property Event.StartUpdateEvent as Long
Starts changing properties of the calendar-event, so EndUpdateEvent method adds programmatically updated properties to undo/redo queue.

TypeDescription
Long A Long expression that specifies the handle to be passed to EndUpdateEvent so the updated properties of the bar are added to the Undo/Redo queue of the chart, so they can be used in undo/redo operations.
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:

within the UndoListAction/RedoListAction result.