Something

<head>
                <script type="text/javascript">
                function go()
                        {
                                box = document.forms[0].order_by_select;
                                orderby = box.options[box.selectedIndex].value;
                                if (orderby) location.href = 'index.php?order_by=' + orderby;
                        }
                </script>
</head>
 
<body>
<?php query_posts('cat=4&posts_per_page=-1&orderby=' . $order_by . '&order=desc'); ?>
<?php if (have_posts()) : ?>
                <form id="order_form" action="index.php" method="post">
                        <fieldset>
                                <table>
                                        <tr>
                                                <td colspan="4" style="text-align: right;">Sort by:
                                                      <select id="order_by_select" name="order_by_select" onchange="go();"> 
                                                      <option value=""><?php echo attribute_escape(__('Select Event')); ?></option> 
                                                      <?php 
                                                      $categories=  get_categories('child_of=4'); 
                                                       foreach ($categories as $cat) {
                                                      $option = '<option value="'.$cat->cat_ID.'">';
	                                              $option .= $cat->cat_name;
	                                              $option .= ' ('.$cat->category_count.')';
	                                              $option .= '</option>';
	                                              echo $option;
                                                     }
                                                    ?>
                                                  </select>
                                                </td>
                                        </tr>
                                        <tr>
                                                <th>
                                                </th>
                                                <th>
                                                        <h2>Title</h2>
                                                </th>
                                        </tr>
 
<?php while (have_posts()) : the_post(); ?>
                                        <tr>
                                                <td class="col_0">
                                                        <?php if (post_custom('book_cover')) { ?>
                                                        <a href="<?php the_permalink();?>"><img src="<?php echo post_custom('book_cover');?>" alt="pic" /></a><?php } ?>
                                                </td>
                                                <td class="col_1">
                                                        <h2><a href="<?php the_permalink();?>"><?php the_title();?></a></h2>
                                                       
                                                </td>
                                        </tr>
 
<?php endwhile; ?>
<?php endif; ?>
                                </table>