Currently, Civil 3D is unable to create a label style expression that can for example do this: {Surface Elevation} - {General Segment Start Z}. This is because the {Surface Elevation} parameter is under the "Surface" label style parameters and the {General Segment Start Z} parameter is under the "Line" label style parameters and Civil 3D does not allow expressions using variables from different feature classes. Please consider adding the capability for users to write expressions like this.
