Excel 2007 : Calculate Peak Usage of Vehicle

Hello All! First, let me start by saying I have limited Excel skills. I can perform simple operations, but the question I am posting is way above my knowledge level.

I've attached a spreadsheet. This sheet tracks the dates and times vehicles in my company were in use in a 5 state territory over a 7 week period. I have tracked the date, the time the vehicle was taken out, and the time the vehicle was returned. This was a manual process with drivers logging the data.

What I am trying to figure out is the peak usage of vehicles in a given state during the course of the study. In other words, the specific time and day the most number of vehicles were out.

For example, on 12/17/09 in NM, the peak usage came at 14:30 when 4 vehicles were out at the same time. I figured this day out by plotting it manually as show below: (the data below got messed up when posting but the first number is the time, 1's indicate if a vehicle was out at that time, and the last number is the sum of all the 1's (gosh I hope that makes sense))

Time In Use at time? (1=Yes, blank=No) Total Cars in use at time
815 1 1
830 1 1 2
840 1 1 1 3
845 1 1 1 3
900 1 1 1 3
915 1 1 1 3
920 1 1 1 3
930 1 1 1 3
945 1 1 1 3
1000 1 1 1 3
1015 1 1 1 3
1030 1 1 1 3
1037 1 1 1 3
1045 1 1 2
1100 1 1 2
1115 1 1 2
1130 1 1 2
1145 1 1 2
1200 1 1 2
1215 1 1 2
1230 1 1 1 3
1245 1 1 1 3
1300 1 1 1 3
1315 1 1 1 3
1330 1 1 1 3
1345 1 1 1 3
1400 1 1 1 3
1415 1 1 2
1430 1 1 1 1 4
1440 1 1 2
1445 1 1
1500 1 1
1515 1 1 2
1530 1 1
1545 1 1
1600 1 1 2
1615 1 1 2
1630 1 1 2
1645 1 1 2
1700 1 1 2
1713 1 1 2
1715 1 1

There is no way I can plot every state and every day for the entire spreadsheet. I'd be here for a month.

In a perfect world the data I am looking for could be displayed in a chart that shows the entire study period. Can anyone help please??? I've been at this for several days and can't figure it out. Thanks in advance for you help and I hope I was able to attach the file correctly.

Cheers, Tony