specialized, simple menus

Okay I have a basic UL/LI menu, with a UL inside the LI for submenus.

Anyway, in the submenus, the first item has a class of “png first”, the last has “png last” and the middle ones have “png”

Therefore, I am wondering how I can get wordpress to read this and create the navigation items automatically while adding.

The current navigation code I have (all html, which is the output I would like wordpress to make)

Basically, all these are PAGES. No categories, nothing. Just parents and children. your advice will be much appreciated!

<ul id="navmenu">
        <li><a href="/" class="png">home</a>
          <ul>
            <li class="png first"><a href="/aboutus.html"><span>About us</span></a></li>
            <li class="png"><a href="/missionstatement.html"><span>Mission Statement</span></a></li>
            <li class="png"><a href="/qualityassurance.html"><span>Quality Assurance</span></a></li>
            <li class="png last"><a href="/contact.html"><span>Contact Us</span></a></li>
          </ul>
        </li>
        <li><a href="/products.html" class="png">Products</a>
          <ul>
            <li class="png first"><a href="/products/breakoutwrenches.html"><span>Breakout wrench</span></a></li>
            <li class="png"><a href="/products/shocksubs.html"><span>Shock Subs</span></a></li>
	    <li class="png"><a href="/products/custommachineparts.html"><span>Custom Machine Parts</span></a></li>
	    <li class="png"><a href="/products/specializedmaterials.html"><span>Specialized Materials</span></a></li>
            <li class="png"><a href="/products/dthbitsandhammers.html"><span>DTH Bits & Hammers</span></a></li>
            <li class="png"><a href="/products/triconebits.html"><span>Tri-Cone Bits</span></a></li>
            <li class="png"><a href="/products/pdcbits.html"><span>PDC Bits</span></a></li>
            <li class="png"><a href="/products/drillpipesandcasing.html"><span>Drill Pipes & Casing</span></a></li>
            <li class="png"><a href="/products/drillcollar.html"><span>Drill Collar</span></a></li>
            <li class="png"><a href="/products/stabilizers.html"><span>stabilizers</span></a></li>
            <li class="png last"><a href="/products/mammothbrushandsampler.html"><span>mammoth brush & sampler</span></a></li>
          </ul>
        </li>
        <li><a href="/services.html" class="png">services</a>
          <ul>
            <li class="png first"><a href="/services/blastholedrilling.html"><span>blasthole drilling</span></a></li>
            <li class="png"><a href="/services/directionaldrilling.html"><span>Directional Drilling</span></a></li>
	    <li class="png"><a href="/services/specialprocessing.html"><span>Special Processing</span></a></li>
            <li class="png last"><a href="/services/customcnc.html"><span>Custom CNC Turn/Milling</span></a></li>
          </ul>
        </li>
        <li class="last"><a href="/industries.html" class="png">industries</a>
            <ul>
            <li class="png first"><a href="/industries/airdrilling.html"><span>Air Drilling</span></a></li>
            <li class="png"><a href="/industries/muddrilling.html"><span>Mud drilling</span></a></li>
            <li class="png"><a href="/industries/mining.html"><span>Mining</span></a></li>
            <li class="png"><a href="/industries/oilandgas.html"><span>Oil and gas</span></a></li>
            <li class="png"><a href="/industries/waterprojects.html"><span>water projects</span></a></li>
            <li class="png last"><a href="/industries/civildevelopment.html"><span>civil development</span></a></li>
          </ul>
        </li>
      </ul>