Immediate Need!!! Help w/ Marathon Timesheet. Issues with calculating time spanning days.

I have an IMMEDIATE NEED for help constructing a spreadsheet that would allow me to calculate a runner's time. I am serving as a Race team Coordinator that will be in charge of tracking multiple runners time.

I will be using a spreadsheet on my tablet and entering time in 24hr format.

The spreadsheet is to:

1. Calculate a runners's Leg Run Time (the time that they begin running to the time they stop)

2. Calculate a runner's Total Leg Time (The time difference between two consecutive runner start times.)

3. Show also show a cumulative time for entire race. (Adding all Total Let Times)

I have attached an example of my spreadsheet for review in Excel 2007 format. If someone could PLEASE help me solve this it would be greatly appreciated. I have 2 days to be able to have my self squared away and I just noticed that the spreadsheet was not working as intended.

Thanks in advance.

Since I will have to enter time for multiple runners, the quicker I can enter the time, the better. It would be nice to just enter the time and be done. Also, there are a couple of other time calculations needed.