Hi, I was wondering if someone could help me out with a SUM question.

A B C D
0C 12345 40
1C 12345 10
1C 12345 10
1C 12345 10
1C 12345 10
0C 23456 20
1C 23456 10
1C 23456 10
0C 89012 25
1C 89012 10
1C 89012 10
1C 89012 10

A brief explanation about the data above: Column C when Column A=0C is
supposed to be the sum of all AND(Column B with similar values, Column A=1C).
However, that is sometimes not the case, as you can see for record 89012 (the
sum should be 30, not 25).

So, what I'm trying to do in Column D is to manually sum up Column A=1C when
Column B=B, then compare it to the corresponding Column A=0C to see if
they're the same.

In Excel terms, in Column D, how do I perform a SUM function with the
following criteria:
Column A=1C -AND-
Column B = similar value

I hope I was clear enough. Sorry if its confusing, I'm not much good with
programming. Thanks in advance!

-Nick