Enter number plate and add 1

Hello!

This is about car number plate statistics on a car park at our airport

Short: I want to know where the cars at the car park are from.
You can view the excel list here:
http://picasaweb.google.de/rauchmanu...08488388496818
We did these statistics with pen & paper until now, however this is a time-robbing thing. I want to enter it digital at the car park right away.


Question:

Is it possible to create a macro that everytime you enter the number plate code like HH for Hamburg it counts + 1 in my cell for Hamburg.
(If you unter HH three times, it counts 3 cars for Hamburg.
The marcro must sort it to the right code and always add 1.



Would be great if somebody knows how to do that.

Greetings from Baden-Baden
manuel