Need help with complex sequential if/then statement

Hi everyone,
I have a these columns:
A B C D
Date Monkey Focal # Start Time
08/22/2014 FJ 1 7:52:00
08/22/2014 FJ 1 7:52:00
08/22/2014 RJ 1 8:52:00
08/22/2014 FJ 2 9:52:00
08/22/2014 FJ 3 10:52:00
08/22/2014 RJ 2 11:52:00
08/22/2014 RJ 2 11:52:00
08/22/2014 MD 1 12:52:00
08/22/2014 RJ 3 13:52:00
08/22/2014 RJ 3 13:52:00
08/22/2014 FJ 4 14:52:00
08/23/2014 FJ 1 7:52:00
08/23/2014 FJ 1 7:52:00
08/23/2014 RJ 1 8:52:00
08/23/2014 FJ 2 9:52:00

Column C is what I am trying to populate.

The Monkey column has many different options (not just the three shown here), as does the start time. What I would like to do is if the date is the same (A), and the monkey is the same (B) and the start time (C) is the same as the row above the cell, then the Focal # (C) should be the same, but when A is the same and B is the same, but D is different from the row above, it should give the next sequential number, then follow the first rule. When A is the same, and B changes, then it should start over with 1 following the same two rules as before. And when A changes, the sequence should start over following all the prior rules.

Is this even possible? =( Thank you in advance to anyone who thinks they can help with this. (Hopefully I explained it properly)

Place a "1" (without the quotes) into C2 under the heading Focal #
Place this formula into C3, and copy down: =IF(A3&B3&D3=A2&B2&D2,C2+1,1)

Hope it gets you going.

Pete

Wow! This forum is wonderful! Thank you so much - this was exactly what I needed. =)

Hi, back again. =( We made our setup a bit more complex and now this solution does not work. I will have one Monkey (Focal) who has severalrows of Excel data under one focal session. This formula has the layout I need:
08/22/2014 FJ 1 7:52:00
08/22/2014 FJ 1 7:52:00
08/22/2014 FJ 1 7:52:00
08/22/2014 FJ 1 7:52:00
as

08/22/2014 FJ 1 7:52:00
08/22/2014 FJ 2 7:52:00
08/22/2014 FJ 3 7:52:00
08/22/2014 FJ 4 7:52:00

I have tried playing with it, but nothing I try gives me the output I need. Can anyone help me further? Thank you!

08/22/2014 FJ 1 7:52:00
08/22/2014 FJ 1 7:52:00
08/22/2014 FJ 1 7:52:00
08/22/2014 RJ 1 8:52:00
08/22/2014 FJ 2 9:52:00
08/22/2014 FJ 2 9:52:00
08/22/2014 FJ 2 9:52:00
08/22/2014 FJ 2 9:52:00
08/22/2014 FJ 3 10:52:00
08/22/2014 RJ 2 11:52:00
08/22/2014 RJ 2 11:52:00
08/22/2014 MD 1 12:52:00
08/22/2014 RJ 3 13:52:00
08/22/2014 RJ 3 13:52:00
08/22/2014 FJ 4 14:52:00
08/23/2014 FJ 1 7:52:00
08/23/2014 FJ 1 7:52:00
08/23/2014 RJ 1 8:52:00
08/23/2014 FJ 2 9:52:00