Need a Script to rest credit-left to 2hour after every two w

Hello my Gurus
Please can any one here help me with a script that can be reset the credit-lift for user on user-manager to the original value every two weeks?
I need it for my school the student will have 2 hour every 2weeks the uptime will be uptime-limit=2w and after that 2 weeks they can still use that username and password.
Thanks.