Troubleshoot [query_posts]

I’m assigning 2 custom fields to all my post,start_date and end_date.
Right now in my main page, i would like to display all the posts which fall between the 2 date. Seems like not post show up after few trials.
Hope someone will assist me here…
Thanks.

<?php
function filter_where($where = ”) {
global $wpdb;
$cur_date = date(‘Ymd’);
$where .= ” ‘{$cur_date}’ >= (SELECT meta_value FROM
{$wpdb->postmeta} WHERE meta_key = ‘start_date’ AND post_id =
{$wpdb->posts}.ID)”;
$where .= ” AND ‘{$cur_date}’ <= (SELECT meta_value FROM
{$wpdb->postmeta} WHERE meta_key = ‘end_date’ AND post_id =
{$wpdb->posts}.ID)”;
return $where;
}

function filter_join($join = ”) {
global $wpdb;
$join .= ” INNER JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID =
{$wpdb->postmeta}.post_id”;
return $join;
}

add_filter(‘posts_where’, ‘filter_where’);
add_filter(‘posts_join’, ‘filter_join’);
query_posts($query_string);
?>