Yeah, SaintDog is right, that sounds like a hack to me. Check out
vBulletin.org for a hack that would allow you to do this.
Just so we don't send you off with nothing, it sounds like the hack PluhNews 1.5, by Kayn [
link] might just do the trick. I have used NewsPro and Coranto on my sites before and switched to PluhNews when vB was installed. I think this might work for you.
Good luck and I hope this helps!