Sidebar post filter

Hello,

I have some problems making a post filter in my sidebar..
I would need to display all the recent posts that are from the same category as the current post, and must have the same value from a custom field as the current displayed post.

I have tried something like that, but thn there is the category problem

<?php $cur_post_value = get_post_meta($post->ID, 'town', true);

$other_posts_with_value = "
    SELECT wposts.*
    FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
    WHERE wposts.ID = wpostmeta.post_id
    AND wpostmeta.meta_key = 'town'
    AND wpostmeta.meta_value = '".$cur_post_value."'
    AND wposts.post_status = 'publish'
    AND wposts.post_type = 'post'
    ORDER BY wposts.post_date DESC
    LIMIT 4
 ";
$other_posts_array = $wpdb->get_results($other_posts_with_value,
 OBJECT); ?>

<?php if ($other_posts_array): ?>

Thank you