driving a Scale factor with an equation

I have an organic shape for a bottle containing liquid. Since you can use the Volume of the SW file in an equation, I thought I'd just create a Scale feature and have SW scale the bottle down by the ratio necessary to achieve the desired volume ( scaleFactor = desiredVolume / currentVolume ).

Unfortunately I can't seem to get an equation to drive the scale factor. Is that possible?

SolidworksGeneral