vary the spring stiffness for inflate simulation

In the process simulating inflating plastic. I was trying to vary the spring stiffness. So each spring have different stiffness. In attached GH file, I was trying to use the distance between mesh vertices to a Nurb surface("A "in the Fig.) to vary the mesh spring stiffness. However, the stiffness of the spring mesh is not varied by the imput distance value.  I was wondering if someone could take a look at the file for me.