Software for restricting GCode to specific regions?

[deonb1]

I would like to use the GCode generated by pcb-gcode in a very specific order:

1) Mill the surface around the mounting holes.
2) Drill the mounting holes (during which I hold the PCB down using
temporary brackets)
3) Fix the PCB to the CNC table surface using screws through the newly drilled mounting holes - then remove the temporary brackets.
4) Mill & drill the rest of the PCB.

However, pcb-gcode doesn't really allow me to specify order. The result is that the mounting holes are scattered all throughout the gcode. This makes it a pain to search for them and edit them away every time I generate new gcode.

So I'd like to run something like a filter/mask over the GCode that performs: "Remove all gcode that are not in these (rectangular) regions" or "Allow only gcode in these (rectangular) regions". Of course it has to allow me to enter a safe Z axis height so that it can move the tool between the allowed regions.

Secondarily I need to make sure the remaining GCode doesn't now have a toolpath that passes over the screw heads that I inserted in this process. (Otherwise I have to make the safe Z Axis so high that the process is incredibly slow).

Any advice on software that I can use to achieve either of this? I must have installed 10 evals today of gcode editors and still haven't found anything close to that.

[neilw20]

Don't use special code, and don't use screws. Or just 2 outside the work area.
Have a pressure brush ring around the spindle that forces the PCB down against the spoil board.
Safe height needs to be high enough for board flex. Maybe 1mm.
Just like the big machines do.

[deonb1]

Ok, but even with the screws outside of the work area, I still need to make sure there isn't a movement path in either the drill file or mill file that passes over that area. (Or if it passes over that area the Z height has to be much higher than usual).

I do use a Z height of around 1mm generally, but that won't clear a screw head. 5mm would clear it, but would add lots of time to the job and be unnecessary in 99.999% of cases.

What's a "pressure brush ring"? Google wants no part of that term .

[neilw20]

Round brush, like off a handheld carwasher scrubber with rotating brushes.
Mount from spindle assembly so that when it moves the drill down the brush pushes against the PCB