New connections logging?

Hey guys,

I'm running a small event in my town, and I am in charge of the wifi/internet. One of the things that I would like to do is register how many new devices register on a specific login. For example,

Every time someone logs a new client onto a login for the network (username guest, password guest), I want to add 1 to a count. Ideally, this count would update every 1 minute, and output to a text file. This is just for record-keeping and to make a pretty graph that shows how successful the event was (showing how many people connected to the wifi that were guests.)

If you know of any program that would aid this I would be very grateful.

Edit: I don't need any data to be taken about the device, I just need it added to a tally the minute it joins the network. I don't even need the device name to show up.

E2: Some info that may help

• AP Type: Cisco
• Potential Max clients 1300