The OnUpdate method is called periodically by the framework once the Button has been loaded, for example when the Tab where the Button is displayed is shown.

This provides an opportunity to run some code periodically within your customization. One typical use of OnUpdate is to determine and set the Enabled property of the Button if using application conditions does not provide sufficient control; note that it is more efficient to make use of application conditions if possible.

Note that as OnUpdate may be called frequently you should avoid lengthy operations in this method, as this would reduce the responsiveness of the application user interface.