Contextual Navigations

I’m hoping somebody can help me out here. I’ve looked at conditional statements for WordPress but I’m not sure if it’s really the solution to my problem. I’m building a site for a local organization and what I need is a contextual navigation.

In essence, if somebody click on “Local Lodges” in the main (top) navigation, I need the side navigation to show a list of links to the lodge pages on my site. In essence the side menu will be the same for any Main Navigation link and/or it’s children.

Does anybody have a suggestion? If I can do this using WordPress’ conditional statements, does anybody know how?