Vary spindle speed dependently of axes speed

I have installed laser that change it's power correspondatly to spindle speed (M3 S1000 - form example)

CNC mashine has periods of acceleration and deceleration. I want to configure laser power in such way:
Formula: Laser Power := Current Axes_XY_feed_speed * Spindle_Speed / Axes_XY_nominal_feed_speed.
Module of Axes XY nominal feed speed - it sets with G1 F600 for example.

So, when machine is not move, laser gives some min_dc value.
It would be vary nice to turn on and off this function with some g-code (FLOOD - form example).

Also my topic for this laser:
Set dirrect speed override

I found documentation for this question
"Extendinc Linuxcnc" and remaping codes. I've looked through it but it seems unfinished.

There is a Sim example for remapping. If you remap the Fcode and set one of the analog outputs with M68 you have apin that can be used in HAL.

Personally, this is where I would reach for a custom component as a few lines of C code would make the calculations you want very easy.