Yes this is simple enough, actually if you look at the sample site (Telerik University
) that comes with Sitefinity that already has a working example. You will notice that it uses a RadTabstrip control for the main navigation and then they have a RadPanelBar on the left site with the "sub navigation" which are the child pages. Basically because Sitefinity uses the SiteMapDataSource you can take full advantage of that to create whatever scenario you need with very little coding.
The sample sites code can be found in the Project Manager of Sitefinity once you have installed it.
Hope that helps.