audo updating AD attributes

Hi,
I am having 2003 domain. I want to be able to store last logged on Computer
/ User account values in some attribute in AD automatically. For example I
have computer1 & user1. When user1 logs in to Computer1, the user1 account
attributes should automatically get updated saying that user1 has last used
computer1. Same way, when I go to computer1, it should show me that the
user1 is the last user who used the computer.
I have seen this working, but not sure how can it be done. Appreciate any
advise or pointers.
Thanks