I am using the "Published To" field in my events so that they are removed from the Events list when they are past the date. This works fine except when people click on a link to that page it is a bit confusing that the page returns a 404 error. Indeed the page is not published and not found, but I would like to return a "soft" error saying this event "is past and no longer valid"

Is there any way to have a special "error" message for my "Event" documents instead of the standard one?