Write an OnExecute event handler to respond when an action in the list fires. 

When the user invokes a client object, the action list’s OnExecute event is the first event to occur in response. If the OnExecute event handler sets its Handled parameter to true, the action is considered handled, and processing stops there. This blocks the execution of any other event handlers or any built-in response by a predefined action class in response to the user action. 

If the OnExecute event handler does not set its Handled parameter to true, the application’s OnActionExecute event occurs next. If the OnActionExecute event does not respond to the user input, the action object’s OnExecute event occurs. Finally, if the action does not have an OnExecute event handler, the application locates a target object and executes any predefined response implemented by the action object. 

Execute 

OnExecute 

OnActionExecute