wp_list_pages nested structure and class inheritance

I am building a menu with wp_list_pages and am having an issue with the class current_page_item and nested uls. What I want to accomplish is have a style that will show the page the current page the user is on.

I am using the current_page_item class which is automatically generated by WP. This works good – I can set a style for this and the current page is highlighted in the menu.

The problem is that all of the children menu items are also highlighted. I just want the top level menu items to be affected.

Here is the code that WP outputs with ‘Services’ selected
(And all of the children of ‘Services’ adopt the current_page_item style – which is what I am trying to avoid):

<ul id="dropmenu">
    <li class="page_item page-item-5 current_page_item"><a href="https://localhost/wordpress/?page_id=5" title="Services">Services</a>

        <ul>
            <li class="page_item page-item-7"><a href="https://localhost/wordpress/?page_id=7" title="Financial Management">Financial Management</a>
            <li class="page_item page-item-31"><a href="https://localhost/wordpress/?page_id=31" title="Your Portfolio">Your Portfolio</a>
        </ul>
   </li>
</ul>

And I am using this code to highlight the menu item for the current page:
#dropmenu .current_page_item a {color:#000;background-image:url(images/curr.gif);background-repeat:repeat-x;}