A third interrupt on UNO

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

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:


For a project that uses the change pin as an interrupt see:-