Windows User logon automatically

I would like to make a hack in wp-login.php that allows me to check the REMOTE_USER server variable passed to my server (an internal one) through the browser then log a new into the system automatically. If their windows username isn’t in the WordPress database then it doesn’t let them logon.

I’ve been trying to farmilirise myself with the code in wp-login.php but haven’t had much luck so far. I’m thinking the code I want to will make use of some of the functions under this code “case ‘login’ :
default:” but I don’t know where to start.

Does anyone have any ideas how I could achieve this?

Thanks for your time.