That is so easy. Start a new relationship!!
I have used it which really works well. But make sure your system is Mac OS X 10.7.5 or later and other information.
It supports trial version, you can take a try at first.
If you rent movies from iTunes, you have 30 days from the time of rental to watch your movie, and 24 hours (in the US) or 48 hours (elsewhere) after you've started viewing to finish it. Once the rental period expires, the movie will disappear from your iTunes library.