Need help with a financial formula

Excel......2 columns.......a date and a price.

How can I set this up so that it looks at the date column and gives me the grand total for all of the transactions in the price column by month.

Know what I mean?

16-Nov-12 100.00
27-Nov-12 100.00
14-Dec-12 100.00
30-Nov-12 100.00


In this small example table here, the November total would be 300 and the December total would be 100, but that's a running total, because the month isn't over yet.

In actuality the durn thing is over 300 rows long.

I wanna link a report to this data that will update the running totals as players are entered, and show the monthly revenue.

Any ideas?