Allow only a user to login per day

Hi!

I am trying to build a login that will only allow a user to log in to the program I am currently working on per day.
So, for example, user 1 will log in today, his 2nd attempt to log in today will stop the program. The user's next log in to the system will be activated tomorrow.

I am using vb.net 2005 and MySQL xampp

Thanks & regards,
Bob