how do I sum a column of data based on criteria in two other columns? I have
three columns of data, one contains account numbers, one dates and the third
data to be summed. The difficulty is that there are duplicate entries and
the account numbers go to 8 digits and I am summing to 6.

customer-project-part Hours Date
A B
C
1234-02-06 20
01/01/06
1234-02-07 20
01/01/06
1234-02-08 20
02/02/06

sum of 1234-02 =40

The account 1234-02-07 is ignored because it is on the same date as
1234-02-06. The situation is that I am adding the total number of hours a
machine is run but there are multiple parts going through at once. So I am
adding only one occurance per project number for each day.


Thanks