Highlight Nevigation menu's Sub Pages

[$urya]

HI, i am trying to high light sub menu when selected just like Daniweb IT Community as it shows: Web Development > web design

i am using site reptile to build site and there they use tags to genertae menu's automatically in DHTML here is it's Structure

style in which current page will be :

<style type="text/css">
.item_active
{
    color:#FFFFFF;
    height:30px;
    background:transparent url('images/hover.png') no-repeat;	
    margin:0;
}
</style>

Menu Generated automatically:

<div id="menu">{%menu_start=1%}
<li><a class="{%menu_ActiveClassName%}" href="{%menu_href%}">{%menu_display%}</a></li>
{%menu_end=1%}</div>

here

class="{%menu_ActiveClassName%}"

automatically set .item_active class to the current page.

but the main problem is with displaying submenu to be highlighted with this here is my website sitemap:

|-Home
|-Download
|-Software
|-Music
|-Movies
|-etc
|-About

if i nevigate to Home/Download/About then these page will be highlighted as they should but when i hover over Download and Select Software/Music/Movies..then these page are bieng displayed but didn't highlighted. i want to do it same as you can see of this community page as web design being highlighted.
Kindly tell me any Suggestion or help if you have with this :)

Thanks and Regards
Surya