Figured it out. It is easier to do using power density rather than field density.
1st define a box around the outside of your enclosure. Using the select face option, select each face of the outer-box. Select Edit Create Object from Face.
Do the same for a box on the inside of your enclosure.
Then using the calculator, define the Power incident on each face of the inner box. In the calculator tool>Copy Vector_RealPointing to the stack. Select Geometry and select a face defined on the inner box; click Normal, click Integration sign, click Abs. Click add - give the function a name.
Repeat for each face of the inner box.
Copy each new function to the stack, click + 5 times. Click add - give new function a name.
Repeat for the Outer box all steps for outer box.
SE=10*log(Power_Inc/Power_Transmitted)
This can now be plotted in a rectangular plot