Hi! Can I use Greek yogurt as a starter. I have a yogurt machine and I am dying to use it.

I love my yogurt machine as well, and I find that the most reliable starter is a live culture I find at my natural foods store: here is a link to the formula I use.
http://thesolitarycook.wordpress.com/2012/01/13/luck-times-3/

As long as it contains live cultures.