How to: Respond to Changes in a UML Model
In Visual Studio Ultimate, it is possible to write code that is executed whenever a change occurs in a UML model in Visual Studio. It will respond equally to changes that are made directly by the user, and by other Visual Studio extensions.
These techniques are unsupported by the UML API. They might not work in future versions of Visual Studio.
Sample code is available at UML: Responding to Changes in a UML Model by using Events and Rules