[oXygen-user] Prevent the writer from entering a certain element

Hi, I was wondering if it be possible to avoid showing an element when the auto-suggest suggests an element for insertion at a particular location. I am planning this to avoid usage of a few elements like "unknown" etc. I understand that I can use CSS to hide elements in the Author view, but I would not like to show these elements in the element auto suggest even if it is valid. Is this possible? Thanks, Nathan