Shading an area on graph between two limits

[adk3rwb]

Hello All, and thank you in advance for your help!

I am using cacti to monitor+graph temperature and humidity readings (Temp, Hum).
Along with the current temp/hum readings, I've defined upper and lower "threshold" data sources (MinHum, MaxHum, MinTemp, MaxTemp).

I am trying to figure out the best way to shade in the area of the graph between MinTemp -> MaxTemp, MinHum -> MaxHum.

Currently I have this working for Temp by adding 2 "AREA" graph items:
MaxTemp (30% alpha, light green) and MinTemp (100%alpha, white)
I graph an area from 0->MaxTemp in light green, then draw an area over 0->MinTemp in white over it.
This works fine, but feels hack-y, and when trying to do the same for humidity, I've run into issues when the ranges overlap.

I'm thinking there must be a better way to accomplish this, and the little bit of research I've done indicates I should look into CDEF's...

Am I on the right track? Any advice/input you have is much appreciated!

Thanks,

Andrew