Handling a framework-specific event and MVVM?

In a WPF application that uses Prism, I have a shell in which there is a docking manager control.

Now I have to listen to an event coming from that docking manager, specifically, when one of its children docking state has changed.

To me, this event should be handled in code-behind as letting the view model do some work against that framework-specific visual control is worse than doing it code-behind.

Question:

Is this the right approach or am I missing something?