In this tutorial we will look at a workflow in Civil 3D to manage and label measure down information for points representing manholes and catch basins. This can often be a tedious and error prone task so our goal here is to get the information into Civil 3D once and treat it as data that we can use for any need rather than manually creating notes as text in the drawing.
In Civil 3D go to the Settings tab of the Toolspace. Expand Point and create a new User Defined Property Classification. This is just the name of a new collection of User Defined Properties that you will be creating.
Next right-click on that new User Defined Property Classification and create a new User Defined Property.
Give the User Defined Property a name. In this example above I called it Measure Down 1 as I may want to have the ability to manage information for more than 1 measure down per point in the future.
Set the Property Field Type to Double. This will allow you to enter numbers that include decimals. You can also decide if you want to include a default value or not.
Once the User Defined Property is defined you need to create an Expression that will subtract the value of the new User Defined Property for Measure Down 1 from the Point Elevation. On the Settings tab of the Toolspace under Point, expand Label Styles. Right-click on Expressionsand select New.
Name the expression and then in the Expression field create and expression that is the Point Elevation minus the Measure Down 1value. Both these values can be found by selecting the Insert Properties button 
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Set the Format result as option to Elevation.
Once the new expression is created you can create a Label Style that uses the new expression value as a text component.
In the example above you can see that the Property IE 1, which is the result of the expression, is being used along with a basic text prefix.
Once the User Defined Property, Expression, and Label Style are created (which by the way can all be saved in your Drawing Template) you can then simply enter the measure down values in the Point Editor once, and Civil 3D will calculate the inverts and use that result in the labels.
