Authentication Variation

Hi

I need to make the user sign an Non Disclosure Agreement (NDA) for the first time he/she logs in. After that i want to check each time a user comes in to c if he/she has signed the NDA. If the user has signed the NDA then he/she should be able to log in else it should keep prompting to make them sign it.

I want to make a variable in the DB wchis indicates if the user has signed the NDA and need to access that variable. I would appreciate if some one could guide me through the process.

Sincerely,
-Jinesh