Maybe somebody else has run into my issue and found a creative and automatic solution.
My setup is as follows:
1) I have a sheet where I capture the project status from 10+ team members.
2) It contains a 'Modified' column.
3) The sheet contains calculations that are updated whenever the sheet is being opened (e.g % of time passed, Earned Value, Planned Value).
The use of the TODAY() function for some of the calculations seems to lead to the 'Modified' cell in each row being updated whenever I or somebody else open the sheet - even without actually/manually changing anything - so I cannot rely on the information from the 'Modified' cell to trigger an alert.
Any other suggestions to trigger an automated alert before I give in and ask my users to manually update a field or a checkbox?
P.S.:
I also tried to use a 'Modified By' column, but it seems to cause the same problem: if I just open the sheet it's my name that shows up as the 'Modified By' user.