has anyone tried this before? and if so, does it work?
You could try an onclick + web bug combo. Listen for onclick on your outbound links, and if you get a click, twiddle the query string of a 1 pixel image somewhere on the page before letting the click complete.
Maybe something like
document.getElementById('someGraphic').href += '?out=' + thisLink.href; return true; to add the outbound activity to your access log.