How to control top menu from side menu

I am developing a web application in .NET 2.0 using the menu control at the top and a navbar from Infragistics on the left hand side. It is supposed to look very Outlookish.

Does anybody have any recommendations on how to control which menu options appear on the top menu based on the navbar group that is selected on the left? The left side is used to choose what area you want to work in, and then the drop down menu at the top will give you all of your function options for that area. Because they are two different web controls I don't know how to check from one what was selected in the other.

Thanks,
Patrick