“Read by <user>” checkbox in posts

Hi. I have been browsing for some help on getting a “read by <user>” field and checkbox option on my blog, but so far I have not found a solution.

I need to know if people have actually read the posts on my blog, hence a checkbox, radio button or drop down menu containing the full list of registered users would be helpful. I would like to get this option integrated into every new post and of course a field where I easily can see the list of users that have read it.

Does anything like this already exist? If not, could someone point me in the correct direction? I am new to both wordpress and php, but I have been playing a lot with the files and I am starting to get a hang it. Afraid this problem is a little too advanced for me though.