mpheval() along Boundaries

I am using the Magnetic Fields no Current module and am trying to extract the H field along a boundary between material A and material B using mpheval. What I am finding is that Comsol is returning an average H based on the node assuming material A and B.

Is there a way that I can specify that I want the values for material A along that boundary. The only way I have been able to get close to this so far is to use mpheval to return the values for domain A then programmatically in MATLAB identify what elements are long that boundary.

I attached a image that might help visual this issue. The boundary between material A and B occurs at the discontinuity in the plot. The function call I am using is:

data.MagM = mpheval(model, {'mfnc.normM'}, 'edim', 'boundary', 'selection', 17, 'Dataonly', 'on');

Thanks in advance for any help,

Brandon