How do I add an area under a curve on a scatter plot ?

[tja26]

I have a scatter plot with a regression line plotted and I want to shade a certain area under the curve - I want to be able to adjust the minimum and maximum x-axis values so that the shaded area will change accordingly.

I have been trying to figure this out from looking at an earlier thread, but am struggling to get it to work (http://www.excelforum.com/excel-char...ter-chart.html).

I have attached the spreadsheet with my data in it. To begin with, I am just trying to create a trapezium to approximate the curve for simplicity. I have drawn on the image the trapezium that I would like to have displayed.

Any help would be greatly appreciated.

Thanks

Tim