Plugin Shadowbox JS & plugin Multiple content blocks

Hi,
I need your help making the shadowbox plugin work in an own created area, “the_block” for example. As long as I got a picture in “the_content” part of my website, also the pictures in the “the_block” part open in the shadowbox, when the “rel” is set.
But as soon as there are no pictures in the content, the shadowbox doesn’t appear in “the_block” part either, although you can see the correct “rel” in the code.
I tried to change the code in the frontend.php (“add_filter ( ‘the_content’, array ( &$this, ‘add_attr_to_link’ ) , 12 , 2 );”…), but failed miserably 🙁
I really hope, you can help me, Thanks a lot!