Need help creating timeline and counting

I actually found this site by viewing http://www.excelforum.com/l/701685-asdf.html . This was very relevant to what I am trying to accomplish. I have an excel sheet and I am trying to count at any given half an hour mark how man employees are parking here. I need to check if they have a car and if they do then count their shift. I need to show a 24 hour period. Any help would be greatly appreciated!.

Thank you
Jon

Hi,

You leave to many things open which consequently leave me with too many assumptions on how our "solution" `needs to be.
Could you share a manual example into your file so we can see what your after.