Ok people, I have just found this tool called AirSnare.
"AirSnare is an intrusion detection system to help you monitor your wireless network. AirSnare will alert you to unfriendly MAC addresses on your network as well as to DHCP requests. If AirSnare detects an unfriendly MAC address, you have the option of tracking its access to IP addresses and ports or of launching Ethereal."
The web site where you can DL is below, have a try and let me know what you think.
hxxp://home.comcast.net/~jay.deboer/airsnare/
