"Mack Neff" wrote...
....
What can I do to make "Validation" stronger so no one can enter anything
but
what is in the list?

You can't do anything that'll ensure no invalid entries. There's no way to
strengthen Data Validation. You could use macros, specifically Change or
SheetChange event handlers, but they require macros AND event handlers be
enabled, and it's easy enough for users to disable macros or event handlers.

The old fashioned approach is the only robust way to deal with invalid
entries: use formulas in other cells to test the validity of entry cells. If
entries are invalid, propagate nothing but errors in downstream
calculations, and use other formulas to display error messages saying what's
wrong. In my experience, giving users garbage out when they provide garbage
in as well as telling them how their entries are garbage is the surest way
of getting them to make valid entries.