I don't think that an area chart would suit, the problem is that my chart has two curves:
The Y axis shows positive values and negative values. The Y axis runs from -5 to +5 with the x axis starting at zero on the Y axis. X axis values run from 0 to 200. I have plotted two curves - one is a positive curve and the other a negative curve. These two curves start at 0,0 and diverge as X increases. I want to shade the areas outside the part of the chart contained by the two curves.
These two curves show the limits of acceptability for a calibration sequence that will be plotted manually on a printed version of the chart. I want to show graphically that if any (manually) plotted point is in the area outside the two curves then that value will show an unacceptable condition.