We want to show two surfaces, an existing ground and a proposed ground, on a cross section. When the proposed ground meets up with existing ground, it would be nice for the line to end. With just existing ground continuing on. The surface is data referenced, and I would like to not break either of them. I thought adding a surface mask would cause the proposed surface to stop at the mask, but that doesn't appear to be the case. Are there any other options for achieving this?