Using g-code values to control PWM

Hello,
 am trying to assign values from g-code (for example when i use M3 F1500) to control the value of PWM (pwmgen.0.value). Any idea what to add to the .hal script (or .ini ?) to make it work ?
Thx, Krokrs

One way could be to set a dummy axis like w. 
If you write G0 W-5.00 and your PWM output is scaled to 10, PWM have 50% output power.

one expample of my used hal and ini. ini section

You can use spindle speed, as you suggest, then the HAL would need something like
Or you can use M67:

Hi, probably missunderstanding.
When I set M1 S1500, the spindle is not moving. Any of this M and S commands, which control the spindle aren´t doing anything.
So my solution is, that i connected PWM convertor and few other things and now am controlling speed of the spindle by the value of pwmgen.0.value.
And now the problem - i need the pwmgen.0.value to read the values from S-commmands. How to do it - i have no clue
Your solution is not working for me throughout in my view it´s because of my bad description of the problem.

Do you want the pwmgen to control the spindle, or to control something else (like laser intensity?)

Can you attach your HAL file?

Solved !
It was just a basic thing - I didn´t watch properly the things & when i fixed one thing, it works. But thanks from help
Krokrs