If you static ip each workstation, define a child network, then run the Domain Stat report for that ip it will give you a sort of monitoring process. Unfortunately, the Domain Stat report has been down for quite a while. I used to use this report to add domains that I wanted blocked for each of my defined networks (office locations) by submitting those domains to their proper category. Now that feature is gone. :-)
I do use a small freebie utility called InternetSpy that keeps a time/date local log of websites visited. You will need to set it to hide the icon from the sys tray. You will need to visit each workstation to pull the log. You will also need to set your virus checker to not flag it.