Custom Post Types – File Selector/Drop down

I am creating a wordpress custom post type using v3.0 and would like to add a file selector/dropdown/combo box which lists files attached to this post. The files can be uploaded using Image uploader, media etc from the wordpress standard toolbar.

Is this possible? I am not using custom template/post plugins but coding my custom post in function.php. Similar to this http://kovshenin.com/archives/custom-post-types-in-wordpress-3-0/

I can add static field and pre-defined combo boxes etc but want to build a combo box with dynamic list of file attached to the post.