How Do I Block Users From Linking Directly to a Post?

Hi,

Here is my question, I have set up on premium section of my website peachesandhotsauce.com. I would like every post in the category "The Top Shelf" to be blocked from anonymous visitors. I put "The Top Shelf" category in the exclude section for the "visitors" membership level. Now the category page is blocked - http://peachesandhotsauce.com/podcasts/othyfm/the-top-shelf/ but if I link directly to the post - http://peachesandhotsauce.com/podcasts/othyfm/the-top-shelf/othy-fm-001-03-23-12-anderson-lawfer/ anyone can see it. Please help!