Not sure if I have the right description here.

What I'm trying to show is the range of possible outcome values around a
mean over time. I actually have something working, but there are a
couple small problems with it and I'm wondering how others may have
accomplished this.

Example he
http://vfdrake.home.comcast.net/~vfd...nnel_chart.png

This would resemble the charts NOAA shows to plot predicted storm paths
(e.g., http://preview.tinyurl.com/6xxyrs ) or something like the below:


| x
|
|
| x O
|
| x O
| x O x
| O x x
+--x--------------------
sooner --- later

The "O"s are the mean values; the "x"s are the upper and lower ranges of
predicted outcomes.

Rather than plotting three lines, I want to shade the area between the
extremes, and draw a line for the mean.

I accomplished this by making the O values as a line chart and the x
values as area charts. The upper x series is shaded grey, the lower x
series is shaded white (effectively erasing the grey below the lower x
series). This works, but as seen in the example my solution limits the
ability to show y-axis gridlines and shows some artifacts.

Any other ideas?