How can I restrict a menu section?

I have xWiki 0.9.840 up and running now. Question: I want to have optional sections of the menu bar appear when members of certain groups are logged in. For example, I'd like to have a restricted space (which I now have), but not have the link appear on the left hand menu unless the user is allowed to visit that space. How can I do this? -- Adrian Hall Sr. Product Line Manager, Administration and Identity Management e. [email protected]; t. +1 (408) 720-3856; c. +1 (408) 667-4977