I was able to superimpose to line graph to achieve a very nice effect. However each graph gets top value of the scale from the highest value in the data set. If you look at the attached image, I had to set the last column in each graph to 10 for them to match correctly.
I need to be able to fix the left scale to 10 as a property of the graph, instead of having to change the actual data set so that they match.
The attached is an image of two graph elements on top of each other.