When you select the To Feature check box in the Distance dialog box (Insert | Dimension | Distance), the Perpen To and Parallel To options in the Orientation area become available for selection. These options tell PC-DMIS to compute the distance between the first selected feature and the second selected feature parallel to, or perpendicular to a certain feature.
If only two features are selected from the list, PC-DMIS computes the distance between feature 1 and feature 2, parallel or perpendicular to feature 2.
If three features are selected from the list, PC-DMIS computes the distance between feature 1 and feature 2, parallel or perpendicular to feature 3.
The feature used to establish the relationship should be a linear feature.