Ummmmm....how about using the Management Console (assuming this is only a single server environment)?
Try this:
* Go to Start->Administrative Tools->Computer Management
* In the left-hand pane, expand Shared Folders
* Highlighting Shares will show you how many client redirections there are for each share on the machine
* Highlighting Sessions will show every user connected to the server, and list how many opens they currently have
* Highlighting Open Files will show you every open file, how many people have it open, and exactly who those people are
HTH