CFCHART question (range in the background)

Hola.

I want to put together a line graph using CFCHART. That part works great. But I also want to display a horizontal band of color that shows the "acceptible range" of values, so that it is obvious to the users when the data points fall outside that range (both above and beyond). All I need is a different background color for just one area of the graph.

But I can't figure out how to do it...

Any suggestions?

Thanks in advance!