How to set search result page by custom field?

hello.
i need help...
i am having a bbpress website, and i want my search results will be sort by custom field.
the cf is "price", and the result need to be display from the highest to the lowest.

this is the code for my search.php
`
<?php get_header(); ?>

<div id="main">

<?php do_action( 'bp_before_blog_search' ) ?>

<div class="blog-heading">
<em class="fr"><?php _e('search resulte', 'huddle'); ?></em>
<h3 class="fl"><?php printf( __( '"%s"', 'huddle' ), get_search_query() ); ?></h3>

<div class="clear"></div>
</div><!--.blog-heading-->

<?php // Include the WordPress loop file
load_template( TEMPLATEPATH . '/includes/loop.php' );
?>

<?php do_action( 'bp_after_blog_search' ) ?>

</div><!--#main-->

<?php get_sidebar(); ?>

<?php get_footer(); ?>
`
this is extremely urgent. i really need help here guys.

i already read a lots of tutorial about it, but still can't do it.