A dimension must be a driving dimension to drive the geometry. Start simple in a new drawing. Place a line. Place a driving dimension on the line. The color of the dimension will be black on a white background. Go to the variable table and create a new variable. Give the varisble a value and leave variable table open. Right mouse click on the dimension and click on Edit Formula. In the Dimension's Formula, key in the name of the variable you added to the variable table. Press Enter. The text of the dimension will change to green. This specifies that the dimension has a formula driving the dimension. The length of the dimension will also change based on the variable. Edit the value of the variable in variable table. the length of the dimension wil change. Regards, Rick B.