Shading Between Two Time Series on an XY chart

[SDruley]

I am wondering if anyone would be willing to help me on the attached file?

[Andy Pope]

Not an easy task. Especially with smoothed lines, time values and missing data points.

Here a is a simple example that you maybe able to use.
http://www.andypope.info/ngs/ng33.htm

Another approach maybe to interpolate a number of points between each know point and use error bars to fill the area.