About Feature Relations
When creating or editing features, you can type an expression in place of a dimension value. This adds a relation that controls the dimension.
You can type an expression in place of a dimension in the following cases:
• When modifying dimensions in the graphics window, double-click the dimension value and type an equation in the dimension box.
• When creating or editing a feature, type an expression in the dimension box located on the tab. For example, when creating an extrusion, you can type an expression in the depth dimension box.
• When editing dimensions using a dialog box, type an expression in the dimension box.