Hi,
I'm far from sure about this but here goes:
When you issue a <FeedHold> Mach enters 'MC_STATE_HOLD'. Thus the GCode interpreter is busy
and cannot process any Gcode.
The only way you can cause Mach to execute Gcode is when 'MC_STATE_IDLE', which can only occurr
if you end the Gcode job or <CycleStop>.
You can test this by loading then starting a Gcode job. Now <FeedHold> and try all the buttons/functions of the GUI,
most of them don't work. That means that the Gcode interpreter chunk is running and therefore the GUI chunk is not.
The only way I could see that would that might achieve what you want is to modify the existing CycleStart() function
in the screen load script, and I may be that you would have a delay whenever you <CycleStart> not just this particular
job.
Craig