e stop and spindle motor

When I first purchased my router it was set up with Mach 3 and I could independently control the power to the spindle motor with a button on the interface. Since changing over to EMC I am trying to get that button set up for the same type of operation. Right now the only way I can stop or start the spindle is using the external e stop or the switch on the router itself. There must be a pin that will trigger the relay that powers the spindle motor independent of physically pressing the e stop. Just trying to figure that out. Any suggestions?

We need more info, like what machime, router, electronic, connection diagram if any, parallel port or other hardware etc etc.
You will need to know what pin controlls that relay, add a line or two in hal and it will work for sure if it did before.
Pictures will also help.