Counting the number of data points in a survey period. Countif statements?

Hi everyone,

I have a large amount of data to get through (50,000 lines), so I'm looking for a function that will help me solve this problem so I don't have to manually "count" all of my data points.

I have surveyed dolphins for various periods of time, so my first three columns are Date (DD/MM/YYYY), Start time and End time (HH:MM). I'm looking to count the number of sightings (events) between the start and end times of each survey period. The sightings are in a column with the date and time (DD/MM/YYYY HH:MM), and each time there was an event, this information was recorded. I have over 50,000 events, but I need the number of events for each time period.

For example:

Date Start Time End Time Event
24/04/2012 10:20 10:46 24/04/2012 10:19
24/04/2012 11:27 12:43 24/04/2012 10:20
24/04/2012 12:56 13:46 24/04/2012 10:20
25/04/2012 10:20 10:46 24/04/2012 10:27
25/04/2012 10:20 10:46 24/04/2012 11:19
24/04/2012 11:28 12:00 24/04/2012 09:14
24/04/2012 12:49 13:10 25/04/2012 10:11
24/04/2012 13:30 14:00 25/04/2012 10:14
25/04/2012 09:43 10:17 25/04/2012 10:16
25/04/2012 10:19 10:30 25/04/2012 10:29

So basically I need to have the number of events per survey period. I've tried to do countif statements that would say something along the lines of, count if date and time of event is in between start/end time of survey period, but nothing I'm trying is working.

Any help would be appreciated!

Okay I've attached the Excel spreadsheet (let me know if it works, I'm new to the forum!)

I'm trying to fill in the "Number of Events" column, by counting up the number of events from the "Events" column that fall between the start and end times of the survey periods (Each survey period is given a "Rec No").