@snb, The problem here is that if I used your formula as it stands I would need to rewrite it every time I changed the method of operation. To overcome this, I combined part of Yongle's concept ( putting a Y or N value in another column ). Using two criteria as you had suggested my formula now reads:
=If(And(A3=A2,F2="Y"),1440*C3-C2,""). This currently works for all but the last line.

@Yongle, "Sleeping on the job" and "135 mins for Crib" Grrrr! Bet you thought I wouldn't notice those ones. I think we need to have a discussion about your future with my company. ( Please make sure your desk is cleaned out before the meeting)

@Paul, What can I say, I agree that in the end I will try to use Access as the back end, but for now I'm in "suck it and see" mode.