I am trying to combine a formula that does two different things; matches
cities, a code for the city, and if it has a match, calculate the difference,
in weeks between the two events.
ex.
Detroit, 1Pa, 04/06/04
Detroit, 1Pa, 06/23/04
Detroit, 1Pb, 08/01/04
Detroit, 1Pb, 11/05/04

I want to match the cities, and if they have a matching code, find out the
time in weeks between the two event dates. Is this possible, and if so,
HOW??? THANKS