one facebook user with one my website user

[sp1r1t10]

I have my website user "M" and I also allow user to connect to facebook account to see his/her wallpost via my website (such as tweetdeck).I allow that my website user have only one facebook account like.\[quote\] User "John" connect with his facebook account name "FbJohn" something like this.\[/quote\]I also design my database to store uid for facebook account for John.\[code\]id uid name11 123456 John Snith22 234567 Mike Bert\[/code\]uid is store when user register on my website, facebook popup ask him to permission access and update uid for user.my problem is when user back and login to my website. I need to check that user use correct facebook account or not?the problem occur when some user use public computer and old user login to facebook before he login to my website.I need to know that facebook correct for uid in database? if not can facebook logout and show new facebook login popup?how can i do this. give me an idea?thank you!