Question restrct user

[anandm]

I m making one s/w.
where i m giving username & password to user and i m allotting time to him/her.
how to write code to authenticate user through network and how to restrict user to that time which i allotted to him so that he can access internet more than that time and also he should he should be able to access internet only when he is authenticated.

I know .net & also database query