The purpose is to create a Surface Spot Elevation label to be used with Volume Surfaces, that would automatically rotate based upon a Positive or Negative elevation values. 
The solutions were achieved with an if/than expression. First an expression is created, here called “Rotation” is built as follows: DEG2RAD(IF({Surface Elevation}<0,-45,45))
- Use the “Surface Elevation” value
- Prefix with an “If” to designate a positive or negative 45
- And because the way Civil 3D calculates angles, add a DEG2RAD function
Next, in the Composer for the surface spot label style, the previously created “Rotation” expression is used for the Rotation Angle
Then, the labels will rotate automatically based upon the underling (positive or negative) surface elevation values. 
Hope you can use this simple application of equations to label components to control visibility. You can see the first part of this post here: https://resources.imaginit.com/civil-solutions-blog/volume-surface-spot-elevations-part-1-color-code-positive-negative-values
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