Could anybody tell me if this is possible?

My example situaton is:
C1:C5 is a list of people's names.

Cells in Column A are Data Validation List based on
=$C$1:$C$5 and drop down choices are made up to A50.

Due to a staff change, text is replaced at C2 with a new
person's name. Now the change reflects in all drop downs
from that point on!

Question:
When I click on any cell less than A51 in Column A that
contains the old C2 name, can an alert message tell me
that this person has left and will not appear in the drop
down current listing?

TIA