Automatically change AD User's password hourly

Hi

I was wonder if there was a script or some kind of way which could reset a specific user's password every hour and save the password to a .txt file or maybe to a SQL table? I found one program however it emails the password rather than saving it to a file (and isn't free). I am using the NPS RADIUS server role and would like guests to have temporary access without having to create and delete an account every time (or have a static password allowing them to rejoin the network if they return).

Thanks :)