Posts, that only "some" registred users can read

Hi,

I’m searching for a pluging, that allows me to add users, who can and cant read whole post. For example – user1 is attached to post1, post2 and post3, but he isn’t attached to post4. User2 is attached to post1, post4. User1 can read whole post1, post2 and post3, but he can only read the excerpt of post4. Same with user2 – he can only read the posts he’s attached to, but he can also see the excerpt of other 2 posts. I want to add manually the users who can read the whole post, that I’m currently publishing, and all others must see the short excerpt of those. Hope you understand me, my English is one of the World’s worsts.

Thanks in advance,
Yuliyan!