Hi
it is possible do do what you describe. The circuit depends a bit on what you have. Is there a charge pump in operation & has it a contact output, or just a logic level?
The Mach reset should be available on OEM button code 1021, so assigning an input pin to produce that code should do the PC reset. The physical button on the machine that operates the pin will also reset a local latched relay that enables the drives.
If you want the PC to drop the latch out, then including the charge pump contact in the latch circuit will do it. Just make sure that 'Charge pump on in Estop' is not checked in General Config.
I prefer to have the latch tripped locally by physical switch contacts, but the charge pump should still be included in the circuit so that a problem at PC or control will stop things dead.
Hope this helps. I may be able to give you a fragment of circuit when I have some time later on.
Tony