definition of maxwell 3d

Dear All

I have a problem defining a Non Model surface in Maxwell 3d V11.1. I want to define a Non Model Surface and use it as a geometry in the Calculator, for example to calculate the magnetic flux via the surface integral of the induction B.

I use the command Draw->Circle to define a circle surface with the proprietary "Non model" set. In this way the surface doesn't force the simulator to start the analysis again. However if I go in the calculator, and then pushing the Geometry button, I don't find the previous defined surface. It seams that the 2D Non Model surface is not recognized by the calculator.

Of course if I set the surface as a Model surface, I can see it in the calculator

Any suggestion ?

Thanks