dagostm wrote...
Hello: I am trying to figure out the average age of a varying
population of employees on 40 specific days over a three year
period.

Is this retrospective, so you know who the employees are? If it's
prospective and since you provide no demographic information other
than the implicit 'working age', you're on your own.

Is there a formula that can be used to determine this without first
calculation everyone's individual age and then using the
"=AVERAGE(RANGE:RANGE)" formula?

You mean give you the average age without knowing the ages of all the
individuals in question at some point in time? No, at least not the
actual average age. If you could possibly provide demographic
information, there may be ways to estimate the average age, but such
estimates wouldn't be actual average ages. Most of the time such
estimates should be reasonably close to the actual average age, but
such estimates could be way off on rare occasions.