Locking Secondary axis to Primary

[grasstoe]

I have been trying to break my new chart that combines stacked bars on the primary axis with their labels on a transparent line graph tied to the secondary axis. The secondary axis allows me to show the labels I want as categories and position them relative to the visible part of the stacked bar (waterfall style) proportionately outside of the bar. The trouble comes when my label positioning is less than or more than the primary boundaries. I can solve this manually by changing the max or min value of the secondary axis, but what I really want is for the secondary axis to be locked to the primary axis' max and min automatically... any ideas?

gratefully
grasstoe