Can you use Excel to automatically calculate the area between two charts?

As with a lot of questions, I find it is easiest to program a problem into Excel if I first understand the math behind the problem.

I don't know how far back this will be taking you, but I expect that somewhere in your early education, you learned some basic geometry, including how to find the area of various quadrilaterals (squares, rectangles, parallelograms, trapezoids, etc.). If we can figure out how to reduce the area between these curves into a shape that we can calculate the area, we can then program that into Excel.

It just so happens that, since x is the same for each point in the table, each interval in the table describes a trapezoid, for which we all should have learned way back when how to find the area (refresher if you need it: http://www.mathopenref.com/trapezoidarea.html) A=h*(b1+b2)/2. In your table h for each interval will be the difference between the two x points for that interval (h=x2-x1). The length of the two bases will be the difference between A and B (b1=B1-A1, b2=B2-A2).

I would probably perform this calculation in Excel in several steps (to make the formulas simple and make it easy to debug):

In row 7: B7=C3-B3 copied across. this will compute h for each interval
In row 8: B8=B5-B4 copied across. this will compute b1 for each interval
In row 9: B9=C5-C4 copied across. this will compute b2 for each interval
In row 10: B10=B7*(B8+B9)/2 copied across. this will compute the area of each trapezoid in each interval
In some convenient cell: =sum(B10:M10)

Note that this will give a signed area for each interval: negative when B is less than A and positive when A is less than B. If you need to ignore these signs, you can use the ABS() function force all areas to be positive.