Load previous/next posts without whole page reload

I have limited the amount of posts displayed from a certain category. This can be seen in the code below (ive cut out a bit of code to shorten it for this post). Anyway so what i would like to happen is when the next and previous links are clicked to display older/newer post ids i would like it to load these without having to reload the whole site.

Im new to wordpress and this is a learning curve, i realise this may require some use of ajax or jQuery. All im after is point in the right direction.

<?php
$page_num = $paged;
if ($pagenum='') $pagenum =1;
query_posts('cat=5&showposts=7&paged='.$page_num); ?>
               	<?php if (have_posts()) : ?>
		<?php while (have_posts()) : the_post(); ?>   

<!-- item -->
<div class="menutest"><h1><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></h1></div>
<!-- end item -->

<?php endwhile ; ?>
<div class="navigation">
<div class="alignleft"><?php next_posts_link('&laquo; Previous Entries') ?></div>
<div class="alignright"><?php previous_posts_link('Next Entries &raquo;') ?></div><p> </p></div>

<?php endif; ?>

Thank you very much in advance!