Thanks for staying with me on this!
The code in your post above works.
Also, Given Tony's example that he posted above, I know I can use the MessageBus as well. I think the advantage of the MessageBus is looser coupling, in that my non-ui class (which is not a viewmodel), does not need a reference to the model.
Basically I have data coming into the app via CAN (Controller Area Network). That data gets put into the mode which updates the UI. That is nice and easy with Simple MVVM :-)
However, there is configuration data I need to push back down to the CAN objects. That is why I was trying to have the model signal the CAN objects that configuration data had changed.
I thought that since the model classes are calling NotifyPropertyChanged, I could intercept that. Hence my post. I still do not know how to do that. However, since something is putting that configuration it into the model, it could also use the MessageBus
to notify objects further down towards the CAN interface. It just is an extra step.
Thanks again for the help!