Why not use Excel as your calculator? - http://blogs.office.com/b...
"If you've entered simple formulas in Excel, such as adding, subtracting, multiplying, or dividing numbers, you know that the formula it creates looks a bit like what you're doing on a calculator...but Excel saves your work, and is much more forgiving. In an Excel formula, instead of having to start over if you make a minor mistake, you can just fix a thing or two without losing what you've typed." - LANjackal