Removes a handler from the event.
"dataEvent_var" is a variable referencing a DataEvent object. | 
        
"dataEvent_var" is a variable referencing a DataEvent object. | 
        
| Type | Description | 
| boolean | Returns true if removal of the handler was successful. | 
| Name | Type | Description | 
| handler | DataEventHandler | The handler object to be removed from the event. |