PurpleheartOklahoma (scroll down)

As you know VA uses fuzzy math when computing several ratings that come up with different total for overall disability rating.  At the attached is a "Link" to downloaded an EXCEL spreadsheet that can be used to enter you individual ratings to come up with the same rating that VA comes up with.  For example an individual may have several disabilities that combined total 120 percent but VA has a 70 % final rating.  It is easy to use.  The bilateral chart is for when both legs and arms are given different ratings which total 10% each, VA comes up with 37 percent, this chart will show you how they arrived at that figure.  After you come up with the bilateral rating it is put into the chart on the right and then the other disabilities are added in.

http://vets.yuku.com/topic/36441/t/Improved-VA-Math-Calculator.html