i want to create a driver that uses an object's volume (not scale) to determine the size of another object.

I know the volume of the object, as i got it from the '3D-Print Toolbox' built-in addon, but when i calculate the volume of the object i can't right-click on it to obtain the data path, so i can't use it for a driver.

if anybody could help me find the right data path or provide a workaround that would be greatly appreciated.