Trying to wire an expression jack in just right

[spectraljulian]

I have a build going right now that I'm almost finished with and I've hit one little snag. 

My build is a microcontroller controlled sequencer, though this post has nothing to do with the digital end, so I'm posting here. 

So the "expression output" is a stereo jack, and it's wired to two photocells on my breadboard.  One wired from ground to tip, and one wired from ring to tip. 


My "expression input" is wired to a 4PDT throw.   One side is wired so that the TRS go to my ADC on my microcontroller so that it can control various parameters.  That takes up 3 poles.


Where I'm running into problems is how to wire it to the "expression input."   If I wire it in parallel, I get sort of the desired effect.  As I move the expression pedal up, it decreases the range of my sequencer. 

But I want it to decrease the range of the sequencer to absolutely nil.

My second idea was to use the 4th pole to disconnect the ring of the "output" from the tip/ring photocell and wire the tip of the input to the tip/ring photocell on the ring side.  My thought being since Voltage in seems to be on the ring, I'd have the expression "in" divide the voltage before the expression out photocells divide it.  This seems to work far less.  Instead of the expression closing out the sequencer's range, the sequencer closes out the expression's range. 

I can't free up a pole on the switch because if I connect the AGND of the microcontroller to the expression out ground, the ADC stops working on my microcontroller. 

Any ideas on how I should wire this without having to source a 5PDT or 6PDT?