Parent pages function

Hi there,
I was wondering if you know what the function would be to add a css file or even a css style only to level-0 pages in the /wp-admin/post.php?post=384&action=edit area in the backend. I plan to use the css to hide the page attributes meta box on the edit pages of level 0 items so my customers can't change the parent of these level 0 pages and mess up the site structure.