how is it possible to change the mod_mainmenu output structure as below by using mod_mainmenu template. Note here class="box1", class="box2", class="box3", class="box4" will fetched dynamically.

<ul class="menu">
   <li class="">
      <a href="#" class="box1"><span>Menu 1</span></a>
   </li>
   <li class="current">
      <a href="#" class="box2"><span>Menu 2</span></a>
      <ul class="box2">
         <li><a href="#">Sub Menu 1</a></li>
         <li><a href="#">Sub Menu 2</a></li>
         <li><a href="#">Sub Menu 3</a></li>
      </ul>
   </li>
   <li class="">
      <a href="#" class="box3"><span>Menu 3</span></a>
   </li>
   <li class="">
      <a href="#" class="box4"><span>Menu 4</span></a>
   </li>
</ul>