WP Query to list posts published between two particular dates

I just want to List the posts published between two particular dates

I found a solution Here http://www.wprecipes.com/wordpress-loop-get-posts-published-between-two-particular-dates

and my code is Here, unfortunately This is not working !!

<?php
           function filter_where($where = '') {
                 $where .= " AND post_date >= '2012-05-09' AND post_date <= '2012-05-11'";
                 //$where .= " AND post_date > '" . date('Y-m-d', strtotime('-30 days')) . "'";
             return $where;
           }
         add_filter('posts_where', 'filter_where');
         query_posts($query_string);
         ?>
                <?php while (have_posts()) : the_post(); ?>    
                     <h1><?php the_title(); ?></h1>
                <?php endwhile; ?>
 

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