Indicates whether a replacement of either the Execute or CanExecute events (or both) have been applied to this command. 
   Namespace:   Autodesk.Revit.UI  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 17.0.0.0 (17.0.1090.0) 
  Since:  2013 
Syntax
Remarks
 This will not indicate if one or more applications have subscribed to the BeforeExecuted event, as this event is not limited to a single subscriber.