Check in/out when only one user account shared by multiple users

We have our account setup simply with one username and password that we share with our users who are not very tech savvy and won't created their own account. I need to have each one of them log in to edit a document. I tried using the check out feature and then logged in via a different browser and it also let's me edit the document at the same time. Is there a way to make it so only one person can edit the file even though we all log in using the same info?

thanks
Justin