Excel Shared Workbook - VBA issue

Hello,

I have created a shared workbook which allows users to enter data through a user form and then run reports based on that data.

There are about 20 users who update information at the same time and I have made sure that each person has their own allocated data tab so I don't get any save changes issues.

To prevent any corruption, I would like to know if there is any code to count the number of users in a file and if there are already say 10 people in the file, a message box will appear to say that they can't update at the moment and to try again in 5 mins.

Is this possible?

Thank you,

Sharon.