In one of my former employments we had the same concept, and I placed it in a read only share on the file server, and made sure that the backup folder for excel was set to something they had rights to (generally speaking //home/excel)
Another option would be to put it in their home folder and then "robocopy" the master each night, so no matter what they got a copy of the master.
Many different options, just depends what works for you.
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