From Xojo Documentation
An ActionSource object calls the PerformAction method of each ActionNotificationReceiver registered with it.
If you implement this interface in your application, you must implement the methods with the parameters as shown here.
If you want to have a PushButton call PerformAction on an ActionNotificationReceiver then you would create a new class (perhaps ActionNotificationTest) that implements ActionNotificationReceiver. In the PerformAction method, you add the code you want to run when the button is clicked (and before PushButton.Action is called). For example:
Now in the Open event handler for a PushButton, you can add your receiver:
When the button is pressed, the MessageBox is displayed.