I find that I first need to understand the math behind a problem before I can program the solution into Excel. From a quick look at Wikipedia, this looks like mathematical or economic elasticity, where elasticity is the slope of ln(y) vs ln(x). I cannot see how the example comes up with the values you say they get. Are you certain the example is done correctly? Once we know in mathematical terms how they come up with those values, it will probably be fairly easy to program that result into Excel. Without understanding the math behind it, I cannot see how they come up with those values.