restricting user login / restricting number of user login

Hello, I just want to say its very good erp program. I'm still customizing it for my own company. And the demands from my accountants! Phew! I'd like to ask if there is any way to restrict the number of users logging into the frontaccounting?

Example:
user admin. If some dumbo go and give the user admin login to other personnel within the same staff level, there is practically no way for us to keep track of who has access and how many people is access it simultaneously, right?

Is there a function where I can set, the user admin to be able to log only 3 limit of the same user-name?

Or, maybe can restrict only a number of users to login.