See reply in post:
[url=http://forums.sketchup.com/t/beginner-questions/21202/5?u=danrathbun]http://forums.sketchup.com/t/beginner-questions/21202/5[/url]
Also, see this thread:
[url]http://forums.sketchup.com/t/point-relative-to-another/24974[/url]