controlling an add on laser to my gantry mill

sorry aleksamc I have no idea what you mean by this, I'm not very good at this and need some hand holding.

May be you doesn't need it properties, so you don't understand.

Imagine that you need to make laser-work and than after that you want to mill and all operations you make from software program.

Ah yes! I understand, but I am using a hardware switch to do exactly that, it simply switches the PMW generated dc voltage out of the G540 from the spindle to the laser and also switches different voltages in to suit each one.
Thanks
Eric