Highlight 1st level pages in Menu when on 1st and 2nd level pages using wp_nav_m

Ok. This might be a weird one.

I’m trying to use the wp_nav_menu to highlight the Main nav when you’re on both 1st and 2nd level pages. In this case, I only want the 1st level pages to be part of the main nav, but I want the 1st level menu item to be highlighted when you’re on a 2nd level page.

For example, the ABOUT tab should highlight when you’re on /about AND /about/about-me. Right now it’s only highlighting on /about.

Here’s the build http://getthere-fromhere.com

Here’s what I’m calling into my header:

<?php wp_nav_menu( array( 'theme_location' => 'header-menu' )); ?>

This is what I have in functions.php:

function register_my_menus() {
register_nav_menus(
array(
'header-menu' => __( 'Header Menu' )
)
);
}

add_action( 'init', 'register_my_menus' );

And here’s the CSS, if you think you need it:

#NavGlobal		{height:67px;overflow:hidden;font-weight:bold;font-size:11px;width:610px; margin:0 auto;}
#NavGlobal ul	{list-style-type:none;padding:0;margin-left:3px;}
#NavGlobal li	{float:left;xbackground:#999;padding:0px;margin:0px;}
#NavGlobal a	{height:80px;display:block;width:98px;color:#6b7b30;text-decoration:none;padding:3px 0px;margin:30px 3px 0px 0px;
						background:url('images/bkgdNav_i0.jpg');}
#NavGlobal a.i0			{margin:20px 3px 0px 0px;background:url('images/bkgdNav_i0.jpg');background-repeat:no-repeat;}
#NavGlobal a:hover		{color:#990033;}
#NavGlobal a.current	{color:#990033;margin:5px 3px 0px 0px;background:url('images/bkgdNav_current.jpg');}
#NavGlobal .current_page_item a{color:#990033;margin:5px 3px 0px 0px;background:url('images/bkgdNav_current.jpg');}