Mapping hosnames to logged in usernames

Hi All.I need to map currently assigned DHCP IPs to the usernames logged on the machine (using windows 2003 Active Directory authentication).

An alternate paid version for doing this task is:
http://www.badblue.com/prodwip.htm ; but I want to try something free first.

OPenNMS…or Nessus plugin? Is something available for accomplish this? I am aware that it’s not an easy particularly in an environment where DHCP assignments are dynamic, but something should be able resolve this issue. 🙁