Spindel on - off conrtol ...

I have a Chinese 3040 cnc machine bought from Ebay a few years ago.
It works great!
it has a 4 axis controller with a spindle controller on the front panel.
There is a plug on the back that goes to the spindle motor (a 24v 400W DC - 12,000 rpm)
I normally turn the motor on and off using the buttons on the front panel.
I would like a way to turn the spindle motor on and off using CNC commands in the program (M03 - M05)
It may be that this unit can not do that.

Has anyone else using this controller been able to turn the spindle motor on and off with CNC commands?

Willee