[development] cck filefield related question

Hi, probably I'm in the wrong place but I try to ask.. I'm using hook_form_alter to present a special form to anonymous users in D6. I got unlimited upload for a cck image field, but I would to limit to 1 for unauthenticated user. I've found this un-answered question in the cck issue queue: http://drupal.org/node/530828#comment-2288010 Should I maybe play with the submit hook? Thanks in advice, Luca