PLEASE HELP ME: query posts???

Problem:

How to create several div’s with different post categories?

I tried a lot, didn’t get more than this. I can create several loops, but the second one doesn’t dissapear when going to the page of the post. I hope you understand and can help me. 🙂 PLEASE!

Sample: http://www.ukkepurk.nl/blog

<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
 <?php if ( in_category('3') ) { ?>
           <div class="post-cat-three">
 <?php } else { ?>
           <div class="post">
 <?php } ?>
 <h2><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>

 <small><?php the_time('F jS, Y') ?> by <?php the_author_posts_link() ?></small>

 <div class="entry">
   <?php the_content(); ?>
 </div>

 <p class="postmetadata">Posted in <?php the_category(', '); ?></p>
 </div>
 <?php endwhile; else: ?>

<p>Sorry, no posts matched your criteria.</p>
 <?php endif; ?>

<?php $myquery = new WP_Query('category_name=last'); ?>

<?php while ($myquery->have_posts()) : $myquery->the_post(); ?>
 <!-- Display the Post's Content in a div box. -->
 <div class="entry">
   <?php the_content(); ?>
 </div>

<?php endwhile;?>

<?php wp_reset_query(); ?>