Negative exponential distribution

Hey Everyone, I don't know why I have never come across this site before, it is very informative!

I am trying to create a simulation model in Excel for a gas station. I am trying to calculate a formula for the time between cars arriving. I need to use a negative exponential distribution, with an average rate of 60 per hour. How would I go about putting this into excel? I really don't have a clue.

Thanks in advance

I'm not a statistician and do not know how exponential distribution works but here's what I do have;

I set up a spreadsheet where you enter the car arrival times in column A. Column B is automatically filled in and Column C is calculated from column B. A, B and C are set as time formatted as hr:mm AM/PM, Column D calculates the difference in minutes and uses the MINUTE function. Excel has an Exponential Distribution function called EXPONDIST(X, Lamda,Cumulative). Use the Help and type in the function name to get more information. Hopefully this will put you on the right track.

ChemistB