Also from Dave Musgrave, who seems to have caught a nice case of the blogging bug, VBA code to prevent users from logging in to multiple companies at once. This can be a big deal if your company is using most of its licenses. Dealing with users who have been denied access because several users are logged in to multiple companies is a real pain. Dave provides a nice way to deal with it.
If you’re not registered for modifier and therefore can’t use VBA, you can of course buy modifier. Alternatively, you can use SQL to provide a list of people logged in more than once. When combined with a well communcated policy and a daily list that goes to say, the CFO, this also does a good job of preventing multiple logins. It’s just not as elegant as David’s solution.