Turn on a LED while extruding (only) (no replies)

Hello,

I have tried to figure out how to turn on a LED when the printer is extrudig filament, but only when its extruding forward.

I'm using Marlin and tried to add a command to light the LED at various places in the code but all I have managed so far is to get it permanently lit or to flicker for a short while.

I dont want to modify the G-codes sent to the priner, or add new ones.

I use this to light/shut of the LED
digitalWrite(59, HIGH);
digitalWrite(59, LOW);

Any ideas how to do this?