How to Notify Another User of an Update to a Read Only File? VBA Excel

[killpaddy]

I have two workbooks; one is read only and displays information for several users to view at once, and the other is an 'update' sheet that users enter information into which is transferred to the read only file (by saving over the file).

Is there a way of notifying a user viewing the read only file that the update sheet has been used and new information is on the sheet?

Thanks