PPTP using MySQL Authentication

Please read and understand first before you bid this project. I have VPS with PPTP VPN installed and it's running good. The PPTP VPN access is authenticate using MySQL. All the details of the users are saved inside the database (username, password, duration, etc). However, the authentication of that PPTP is only based on username & password. I cant limit the user account using the duration. I try to have PPTP working like PPTP VPN. The sequence should be like this: 1. User try connect to the server through PPTP 2. The server will look into the MySQL database for the account with the correct username, correct password and duration > 1 3. If all the details are true, the PPTP will connect, otherwise it will reject the connection. Basically I would need someone to make the above request fulfilled and teach me on how to do it. I will pay you completely when it is completely working and I fully understand how to do it for later times.