limits: how to determine the hourly queries executed by a particular Mysql user

I'm trying to implement a quota system based on the user in mysql to limit MAX_QUERIES_PER_HOUR for a particular user. I have an option to set this limit through MAX_UPDATES_PER_HOUR 10.
But my problem is that I want to know how many queries a user has executed this hour. I followed this thread, but this is for the global statistics of dba. I want this information for each user in my database. I'm sure that mysql is storing this schema somewhere, but after a lot of examining some of the databases as information_schema , performance_schema , mysql I can not figure out how it will be achieved.