Archive Links

Hi,

I use this code to get the archives to show up in y sidemenu on my blog:

<div id="archives" class="dbx-box">
        <h3 class="dbx-handle"><?php _e('Archives'); ?></h3>
        <div class="dbx-content">
          <ul>
            <?php wp_get_archives('type=monthly'); ?>
          </ul>
        </div>
      </div>

I would like to only show the archives of the last 6 months, how do i do this?

thx