Respond with access-accept when password incorrect

Hi We have guest broadband user accounts. I would like RADIUS to respond with access-accept on PAP even if the password is incorrect. I will then write to the database to indicate the session has an incorrect password and allow the PPPoE to connect to the internet. This will allow the agent to access the CPE to update the password. What is the best way to achieve this, that is to respond with an authentication success even if the password is incorrect for a specific username? Regards Steven