Event for rendercontent selected

Is there an event I could connect to when a RenderContent (for example an Environment object) was selected or lost selection in the Environment Panel (same for Materials with Material panel)?

Or is it possible to check in any other way when my Eto collapsible section should be updated?

I would like to add my own control section (eto) to the Material/Environmnet panel, and I can not find anything which triggers when I change the selection.
The same with the Eto form, I overwrote the onShown/ResumeLayout/onLoad etc funcs, but these are called only at the beginning.


Ok, I think I can see now…
I have to use the eto form DataChanged event.