I have a spreadsheet where I have 5 columns that only times are supposed to
be entered. Is there a way that I can keep people from entering anything
other than times - ex. "none", "n/a", "xx", etc. Numerous people enter data
on this sheet and I have told the many times not to enter anything except a
time, if they don't have a time to leave it blank but it doesn't help.

I already have one validation in there.

Thanks for any help.