wrapping html around parent links only

I am creating a custom theme for a client and am having trouble figuring out how to wrap a <div> around the top level link, and wrap the linked text in a span, but only for the parent pages in my navigation menu, like this

<li id="community">
	<div class="parent">
		<a href="#"><span>Top Level Page 1</span></a>
	</div>
	<ul>
		<li><a href="#"">Sub Page 1</a></li>
	</ul>
</li>

I’m a designer, and know very little about PHP constuctors.
I am working in the classes.php, but can’t figure out how to treat the parents differently from the children. Can anyone offer me some guidance.
Thank you,