Although all Configurations of a design will have a common set of dimensions, the values of those dimensions are parameters whose values can vary from Configuration to Configuration

How to use the Equation Editor

1.  Select the Equation Editor tool in the Assembly Tools section of the Assembly tab. 

 2. The Equation Editor dialog box will be displayed. For each dimension the Name and Comments fields will be the same between configurations. The Equation field, which is either an equation or a specific value of a dimension, can vary between configurations.