The function called by Fusion when the associated event is fired.
"activeSelectionEventHandler_var" is a variable referencing an ActiveSelectionEventHandler object. | 
        
"activeSelectionEventHandler_var" is a variable referencing an ActiveSelectionEventHandler object. | 
        
| Name | Type | Description | 
| eventArgs | ActiveSelectionEventArgs | Returns an object that provides access to additional information associated with the event. |