RaisePropertyChanged from within Register

Question

I'm having a problem getting the RaisedPropertyChanged to work from inside a Messenger registration action in my Windows Phone 7 app. Am I missing something?

        Messenger.Default.Register<NotificationMessage<IList<TouchPoint>>>(this, message => 
            {
                MyList.Add(new ListItem
                                        {
                                            Number = 1,
                                            TouchId = PlayerFingers2.Last().TouchId + 1,
                                            Position = new Point(PlayerFingers2.Last().TouchId*10, 0)
                                        });
                RaisePropertyChanged("MyList");
            });