Increment div id in functions.php (or else) ?

Hi,

I use functions.php to help me theme a sidebar:

<?php
if ( function_exists('register_sidebar') )
	register_sidebar(array(
        'before_widget' => '',
        'after_widget' => '</div></div>',
        'before_title' => '<div id="test1-header" class="accordion_headings" >',
        'after_title' => '</div><div id="test1-content"><div class="accordion_child">',
    ));

?>

But I would like each div id to increment to allow a javascript to his job properly.

First widget is:
test1-header
test1-content

Second widget becaumes:
test2-header
test2-content

Third widget becaumes:
test3-header
test3-content

etc…

How can I do this?

Many thanks for your time and help