Hey Joshua,
you may be interested in this (by the way there is a search function in this forum)
You could try it out and enter M8 into the MDI (M9 to switch it off)
Using the M8 (Flood coolant on) command, however, is a misappropriation, since it is the command to turn workpiece flood coolant on. Usually a dust collection system is turned on when the spindle runs, i.e. by the VFD, or by the CNC controller on M3 (Spindle control).