Specific Loop For 2 Within Each

i use this code in my portfolio http://pocketapps.co/

<?php $args = array(
                                    //your argument code
                                );
            query_posts($args);?>

            <ul>
                 <?php  
                 $ls=0;
                    while ( have_posts() ) : the_post(); 
            ?>
                    <?php if($ls%2==0): echo '</li><li>'; endif; ?>
                    <div class="app">
                            //your code here

                    </div>
             <?php 
                $ls++;
                endwhile;
                wp_reset_query();
             ?>
            </ul>