Homebrew PCBs

Hello...

I looking for isolation mill software. There are few available to do 
basic isolation mill or vonroi. But I look for software that can use 
different mill cutters (different width).
For example I have 4, 16 and 40 mil cutters.

I wan't to mill isolation trace with biggest mill possible. When there 
are not enought space then use smaller mill. So if there are 10 mil 
space I should cut 3 pass overlaped with 4 mil cutter but 20 mil space 
with just two pass of 14 mil instead at least 5 pass with 4 mil.

I think this is must if I want large cooper area to be removed.

Does somebody know for that one? (I know LPKF mills use that technique)