Sharing files across different users

I am after a simple way to share files across different users on my Mac.

EG, my employer and I have separate user accounts on the same iMac.
Throughout the morning I frequently update a particular spreadsheet. When I go home for the day at lunchtime, he also needs to access and update this spreadsheet from his own user account throughout the afternoon.
I saved this file into the public folder and thought that he would be able to pick it up from his user account and that it would be up to date with the changes I had made in the morning but this is not the case.

Help?

Hello,
Perhaps this will help.