I am trying to put together a chart that creates "cliffs" when I change from
one value to another. For example I have the following data:

6/1/2008 350
6/23/2008 350
7/18/2008 350
8/1/2008 400
9/1/2008 400

What I want the chart to show is a flat line at 350 from 6/1/2008 to
8/1/2008 and then a flat line at 400 from 8/1/2008 until 9/1/2008. Besides
adding a dummy line into my row at 8/1/2008, is there another way?