IK Spine squash/stretch volume attribute?


Hello, I have a question,
I have a spine setup with IK spline handle and applied multiply divide nodes for squash/stretch. What could we do in order to enable/disable volume preservation? I simply used set driven key for that volume node (enable=divide / disable=no operation), but it just turns off and on the attribute, so it’s like an on/off switch. What I want is to be able to make change between volume and no volume with smooth values. Like smoothly changing the rotations in IK/FK arm setup. How can this be done?