Help needed with Monophonic script with Chord detection

Grind Inc

Is it possible to make a mono script that disables itself when three or more notes are played together. 

So, when playing melody (mostly two consecutive notes overlapping) it will cut the last one off and keep the instrument mono. But if at any time three (or more) notes are played together, it shall let them pass through (detection could be set to 50ms or so) 

It will reset itself when all notes are off or if only one note is played. 

Thanks