How do I get the Stop Time to work?

I'm trying to get an iTunes purchased (protected) movie to only play a certain section of the movie. I'm running iTunes 10.7 on a Macbook Pro w/ Mountain Lion.

I select the movie in iTunes, get info, go to options, enter a start time and enter a stop time. When I play it, the movie starts at my designated start time, but won't stop at the designated stop time. It just cruises right through it. I tried doing this on the movie in the library, and I created a playlist with the movie and they both behave the same.

Is this a bug, or am I doing something wrong?