A third interrupt on UNO

Hello,
I'd like to know If there is a way to add a third interrupt on UNO.
Thanks

The two external user interrupts available on the Uno are certainly the easiest to use. However all pins can be made to generate interrupts using the correct software commands. I haven't played with them but here seems to be a good writeup that goes into all the gory details about using pinchange interrupts:

http://www.arduino.cc/playground/Main/PinChangeInt

For a project that uses the change pin as an interrupt see:-
http://www.thebox.myzen.co.uk/Hardware/Crazy_People.html