I have two cells for entering a date, "Start Date" and "End Date". I have
used Data Validation/Date to restrict both cells to only allow entry of
dates, and have also set "End Date" to be = start date to prevent a user
from entering an end date that is before the start date.

Is there a way to also restrict the "End Date" cell to only allow a user to
enter a value if there is a value in "Start Date"? Basically trying to force
the user to select the "Start Date" first.

Any suggestions would be much appreciated!