CCK enable dependent fields

Hi,

I've been looking through the following problem with no success so far. Let´s say I got a content type called 'Resources'. A 'resource' has a title, description, some classification (like image, article, tutorial, etc) and other cck fields. I want that when user selects 'image' from the dropdown field, then the cck imagefield gets enabled. How can I achieve this task? Thanks.