Thread Subject: real time object detection

Hello,
I'm new to object detection, my purpose is to detect cars position and number in an image in a fast way.
I read about viola-jones algorithm, that seams to be the state of the art for face detection.
I found this on FEX
http://www.mathworks.com/matlabcentral/fileexchange/19912
but I don't know how to use it.

could someone give me some guidelines on how to approach the problem?
is it possible to adapt this algoritm to detect other object than faces?