You are adjusting the altimeter QNH setting to compensate for colder than standard temps or am I missing something?
When operating in a colder than standard atmosphere the Honeywell FMS calculates the higher crossing altitudes with the Temp Comp feature. We leave the altimeter setting alone and add altitude accordingly to cross the fixes at a higher indicated altitude which equals the original crossing altitude adjusted for error. The FMS takes the guesswork out of it.