thats a very vague question. what specifically should the new button do? there are many different ways a menu button can "interact with the backend"
do you just want an admin link?
<li><a href="../../../admin/index.php">Admin</a></li>
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.