Allow user to sort post

Hi guy… by query_posts I’ve listed my posts.
So, I would allow user to change order the list by parameters like “author” or “custom field”.
Now, I’m writing this code:

<?php $sort= $_GET['order'];
if($sort == "A")
{
$order= "orderby=title";
}
if($sort == "B")
{
$order= "orderby=author";
}
?>

<?php get_header(); ?>

	<div id="content" class="narrowcolumn" role="main">

<h2><?php the_title(); ?></h2>

<a href="?sort=A">title</a>
<a href="?sort=B">author</a>

<?php query_posts($order.'&order=ASC');  ?>

<ul>
<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>

<li>	<a href="<?php the_permalink() ?>" rel="bookmark" title="<?php printf(__('Permanent Link to %s', 'kubrick'), the_title_attribute('echo=0')); ?>"><?php the_title(); ?></a></li>

		<?php endwhile; endif; wp_reset_query();?>
</ul>

But it doesn’t works… How can I do!?