Column A is just an ascending list of dates of every day from 1/1/1970
to today. Column B are data associated with each day.

Elsewhere on the same worksheet I would like to be able to enter a
date in one cell, a number in another cell (let's call the number
"N"), and in a third cell have a formula that takes that date and
number, looks into the above data, and calculates an N day average of
the Column B data from that date forward.

Any help would be much appreciated.

Thanks