How to check which users have the file open?

[adds007]

Hi,
Is there any way I can find out who has the shared file open on their computer?

Why?
I wrote a program thats used by lot of people at our company which references an add-in (.xla file) to use it's code functions. In other words, 50 ppl could be referencing the exact same add-in on a network drive at the same time. I just realized that I can't do updates to the add-in if there is anyone who has the file open and referencing the add-in. SO before i update my add-in I need tell users who have it open to save and close for a second while i update the add-in and they can start again. I was hoping one of gurus can help me find out a solution to this problem, as they always have

Thanks