Jon Peltier wrote:
For your area series, plot the lower one as the lower line, and the upper
one as the difference between the two lines, then use the stacked area
option. Then format the lower series to have no fill, and you'll be able to
see through it.

I wrote about just this charting effect in this article:
http://pubs.logicalexpressions.com/P...cle.asp?ID=590

That's perfect! Thanks for the tip.