How to add to the subnavigation in a single group display.

Hi,

Assuming I login as admin, when I select a single group (from the list of groups), there is a sub-navigation bar that displays Home|Admin|Forum|Members|Send Invites under the group avatar. Question I have is: How do I add a new item to this sub-navigation menu (I'll be using a parent-child theme framework so I won't edit the orignal packaged theme). For instance in addition to the item I've shown above I would like to add the item "What's New", which would be visible to admins, and non-admins alike. Please advise.