Assistance with Counting with Time + Date Criteria

[gadgetboy76]

Hello, I have tried for the better part of the day to come up with a formula or combination thereof to count the # of instances (rows) with the following criteria.

a. for each day
b. by 30 minute intervals starting at 12:00 AM
c. the number of rows

For e.g., on 9/02/2011
- 2 rows between 8:30 - 9:00AM
- 2 rows between 10:00 - 10:30AM
- 3 rows between 10:30 - 11:00AM

etc.

Thanks in advance for any assistance that can be provided!