[jQuery] very simple addClass question for Accordion

[jQuery] very simple addClass question for Accordion


Hi, I am doing an Accordion using the screencast tutorial by John
Resig.
I already have the menu working but need to add flavor to it, first
let me explain that I have added a span class in the dt like so:
<dt><a href="/">
<span>My Menu</span></a>
</dt>
The reason for it is because I have a background image for 'dt a', and
I want to add another arrow up or down image in 'dt' so when the menu
is visible, it shows 'arrow-up', otherwise 'arrow-down'.
I have this for 'arrow-down' for hidden menu:
dt a span {background: url(../images/base_images/icon-arrow-down.gif)
no-repeat left center; padding-left: 20px;}
but I don't know exactly where and how to addClass for 'selected' so
that I can show the 'arrow-up'.
Here is what I got but it added all 'dt a' a 'selected' class.
     jQuery(document).ready(function($){
              $("dl#narrow-by-list> dd:not(:first)").hide();
$("dl#narrow-by-list> dt a").addClass('selected'); /how do I modify
this line ?
$("dl#narrow-by-list> dt a").click(function(){
            $("dl#narrow-by-list> dd:visible").slideUp("slow");
            $(this).parent().next().slideDown("slow");
            return false;
        });
    });
Any pointer is greatly appreciated.
sutra