Pass Windows credentials

Hi everybody, i'm trying to do an hard stuff..... I want to create a PHP page where users can authenticate themselves passing their Windows (XP or 2000) logon credentials trasparently. So, if i've made logon on my workstation with "username" and "password" i want to catch them and reuse to give them access. This stuff will run on a Linux Slackware box with Apache 2.2.4 - PHP 5.2.4 and Samba 3.0.26a Somebody can help me?! Thanx a lot! Simone Nanni ICT Technician A.O.U. Policlinico Tor Vergata Viale Oxford, 81 00133 - Roma - RM - Italy