Hello Chuck. I tried your suggestion, but it does not work. It just displays the raw code ([ad]http://www.mydomain.com/banners/rotate-banner.php[/ad]).
Some other things I've tried that do not work either:
 Regular HTML hyperlink in title (<a href="http://www.yahoo.com">LINK</a>)
 BBCode in extra field as you suggested.
 HTML in extra field.
None of these things produced satisfactory results. Just shows the raw HTML or BBCode. Do I have to enable or disable something somewhere else?