I have found this great facebook like liughtbox script on the net and it works perfect when I have a link to trigger it:

<a href="mypage.php" rel="facebox">Popup Lightbox</a>

Is there anyway I can make this trigger when a page is loaded or refreshed?

I think this is the important part:
Code JavaScript:
jQuery(document).ready(function($) {
          $('a[rel*=facebox]').facebox({
            loadingImage : 'loading.gif',
            closeImage   : closelabel.png'
          })
        })

Hope somebody can help me... Thanks in advance ;.)