You can subscribe to the IObjectScope Changing event. This even occurs when an persistent object is about to be changed. There you can perform your logic and if everything is fine you can allow the change to be done. If you, based on your business logic, decide that this change should not be done you can cancel the event by throwing an exception.
IObjectScope scope = ObjectScopeProvider1.GetNewObjectScope();
sender, ChangeEventArgs e)
//bussines logic goes here.
Note that you have access to the changed field via the OldValue property of the ChangeEventArgs.
All the best,
the Telerik team