I have a page that looks like this: /airport-authority (page id 102)

And that page has 6 children, one of which looks like this: /airport-authority/about-us/

And then that page has children, one of which looks like this: /airport-authority/about-us/executives

What I want to do is display a sidebar sub-navigation that displays the children (executives) when the parent is active (about-us).

That is easy enough to do when you are getting it from the root (using RootChildren). But I need a configuration that sets /airport-authority (page id 102) as the root.

I imagine that the answer lies in a configuration of Root, Skip, Depth but I can't figure it out for the life of me.

I hope I've explained it well. 

Thanks,
Aaron