Charlieplexing w PWM pins

I had an interesting idea...

Has anyone ever tried charlieplexing using the PWM pins? CP works because the microcontroller pins are 3-state (high, low, off), but the PWM pins have effectively FOUR states (HIGH, LOW, off, PWM(n)); If the PWM frequency is significantly higher than the multiplex frequency (not as easy as it might sound, actually), you might be able to do a very easy variable brightness LED array of up to 30 LEDs... (and of course you can do the same thing with a multiplexed array of Nx6 LEDs, with somewhat more control...)

actually it wouldn't quite work as expected. PWM is a square wave as you might know, going from 0 to 5v and back to 0 in a manner of milliseconds. when its at 0v led 1 would light (the pin sinks current ) and when its at 5v led 2 would light. so, you'd have both leds light dimly

Ah. I was think one shared pin at +5, one shared pin PWM (GND/+5), everything else off (one LED at a time mode.) I don't see how more than one LED would light at all.

Your scenario would defineately come into play if I were t o try a whole row of LEDs at one time...