Nofollow for all external links?

Hi all!

I’m looking for a plugin or modification that’ll mean *all* external links have a nofollow tag applied to them. I’m aware this is already done for comments, but I need to do it to links in posts, sidebar etc.

You’re probably wondering why – because I’m taking part in an SEO contest.

If anybody can help I’m not of much use financially but can give you a PR3 (doesfollow!) link back.

Thanks!