[Plugin: Invite Friends] Invite tracking

With this plugin, is it possible to track which users are sending out invites? I would like to hold a contest on my site, every time a user registers from an invite that gives the user who invited the new registrant a chance at winning a prize, the more people that register the better your chances at winning the prize.

http://ww.wp.xz.cn/extend/plugins/invite-friends/