Microsoft Licensing Help

Hello,

I started administrating a new Windows network running 4 Windows 2000 and 2 Windows 2003 servers. I am trying to get their licenses in order.

How do I figure out how many CALS to purchase to get the company legally up to date?

Is there a way to calcualte how many users are hitting each server? From there, do I just purchase CALS based on my findings?

Please help.

Thanks!