One of the more advanced SOLIDWORKS modeling techniques is using equations to drive sketch dimensions. For example you can create a linear hole pattern that derives the spacing and number of holes from the overall length. Let's assume we want .5" spacing from either end, and roughly 6" spacing between holes on a part. To do this create a hole wizard feature on your part. Place the first hole on the part and use a linear sketch pattern on the point. The linear sketch pattern needs three contraints. Direction, instance count, and space between instances. Create the following equations to drive spacing.
When the overall length of the part is changed the number of holes and spacing will update automatically.
Jordan Nardick, CSWE
Computer Aided Technology, INC.