Concurrent Useage calculations help needed

Hello all

My name is Eric and i've come across a problem re: Concurrent Useage that I am hoping someone is able to help me out with. I have done a search and almost found what I was looking for but the equation did not work for me. (The similar question: http://www.excelforum.com/excel-work...ent-calls.html)

What I am able to pull as data is specifically:

MM/DD/YY 00:00am/pm

I have a Start time and End time and need to find the number of instances where those times overlap. The catch is that I have some start times and end times that end in the same day, and some end times that end many days later.

What I am working on is a pool car system where there is a fleet of vehicles that are checked out at various times for an unknown duration. The start time is the time someone is requesting a car and the end time when they feel that they will be done so the requested time could be a few hours or many days.

Is anyone able to assist? I appreciate any and all help anyone can give, thank you so much!

-Eric

This is a very small sample with my manual calculating/looking:

Reservation Start Reservation End Number of Cars Reserved
03/01/11 11:00am PST 03/01/11 2:00pm PST 1
03/01/11 2:00pm PST 03/01/11 3:30pm PST 2
03/01/11 2:30pm PST 03/02/11 9:00am PST 3
03/01/11 3:45pm PST 03/07/11 3:45pm PST 4
03/02/11 10:00am PST 03/02/11 12:00pm PST 3
03/02/11 11:00am PST 03/02/11 12:30pm PST 3
03/02/11 12:15pm PST 03/02/11 1:30pm PST 4
03/02/11 12:15pm PST 03/02/11 2:30pm PST 4

As you can see, there are multipe overlapping dates and times of when the cars are checked out (when their reservation starts and when it ends). I am trying to figure out how to calculate this.