Combining Values In Multiple Lines

I receive a monthly report containing a list of people, and how much is being paid for certain services. The company that sends me this list is preparing to adjust their rates and it will be retroactive back a few months.

The way they plan on doing it is by means of taking a credit back several months, then "re-paying" the correct rate. The main data will include the month for which the payment (or credit) is being made, the person's unique identifier, as well as the amount.

Here's a sample of what it would look like:

Name, ID, Month, Amount
John Doe, 123, 04012008, 25.00
John Doe, 123, 03012008, -20.00
John Doe, 123, 03012008, 25.00
John Doe, 123, 02012008, -20.00
John Doe, 123, 02012008, 25.00

So basically the above shows they paid $25.00 (correct rate) for April 08, then they took back $20.00 the prior two months (the old rate) and paid the correct rate right afterwards.

In what I need to do, this is going to be a lot of work. Is there a way to programatically merge the amounts given the member's unique ID as the "key field" as well as the same month? So it might look like the following:

Name, ID, Month, Amount
John Doe, 123, 04012008, 25.00
John Doe, 123, 03012008, 5.00
John Doe, 123, 02012008, 5.00

Just giving the sum of the amounts for a the given people in the same month?

I'm pretty good with VBA but this one is stumping me.