Sharing a workbook
 

I need to share a document on a central server so several users can update at
the same time. I've used spreadsheets before where when the document is
saved it'll show my changes and their changes highlighted in another colour.
And if you both add a new entry onto the same line it will allow both entries
one after the other, rather than just allowing one entry to be saved. I've
tried using the 'share workbook' function but I can't seem to get it to work.
Does anyone know how? Thanks.