Sum orders by 15 minute periods

I have 1 year of Oracle table data ready to go into Excel. In Execl I'd like to count orders by 15 minute periods (buckets, on the quarter hour). Some 15 minute periods have many orders while some have 0. Is there an Excel function (or a series of a few steps) that will look at column A & B and populate subsequent columns in this way (i.e., columns E & F below)?

Original Data Columns
A (raw data timestamp) B (orders)
************************* ************
1/1/2010 1:05 AM, 1
1/1/2010 1:11 AM, 1
1/1/2010 1:20 AM, 1
1/1/2010 1:32 AM, 0
1/1/2010 1:48 AM, 1
for a whole year
...

Interim Columns (I supose would be necessary)
C (beginning minute
timestamp of buckets) D (orders)
************************* ************
1/1/2010 1:00 AM, 1
1/1/2010 1:00 AM, 1
1/1/2010 1:15 AM, 1
1/1/2010 1:30 AM, 0
1/1/2010 1:45 AM, 1

E (the ultimate goal column) F (orders aggregated into proper th bucket)
********************************* *************************************************
1/1/2010 1:00 AM 2
1/1/2010 1:15 AM 1
1/1/2010 1:30 AM 0
1/1/2010 1:45 AM 1

The purpose is to graph E & F for certain high volume order days of the year.
Thanks in advance!

Thank you for the pivot table solution. My objective has changed a bit so I'm now wondering if there is a programatic solution in my situation. The data looks like this - well actually 4268 rows (3 days) in total, but here's an exact 15 minute subset:
01/31/2011:00:00 1
01/31/2011:00:01 0
01/31/2011:00:02 2
01/31/2011:00:03 0
01/31/2011:00:04 1
01/31/2011:00:05 3
01/31/2011:00:06 1
01/31/2011:00:07 2
01/31/2011:00:08 2
01/31/2011:00:09 0
01/31/2011:00:10 1
01/31/2011:00:11 0
01/31/2011:00:12 0
01/31/2011:00:13 1
01/31/2011:00:14 2
...
I'd really like to be able to sum Column B by 15 minutes intervals based on the Column A character/string timestamps. (perhaps I would need to convert Column A to a real date/time format first?)

I'm picturing code that would place grouped counts in rows below the source/input rows like this:
01/31/2011:00 16
01/31/2011:15 n (for the next set of 15 minutes/rows)
... (and so forth)

It would be really great if I could also adjust the code to generate this by 5 and 10 minute intervals also, such as (5 min):
01/31/2011:00:00 4
01/31/2011:00:05 8
01/31/2011:00:10 4
...
and (10 min.):
01/31/2011:00:00 12
01/31/2011:00:10: n
01/31/2011:00:20: n
...
I would be happy to post this in the Programming area of this excellent forum if that is appropriate. Thank you.

This solution is very helpful. The resources under recommended reading will be useful as well. Thank you!