If I'm starting a company, don't I want R and E to satisfy an inequality (and one in a particular direction) instead of an equation?
More seriously, Excel has many problems that make it unsuitable for anything that might require statistical analysis. See for example B.D. McCullough and Berry Wilson, "On the accuracy of statistical procedures in Microsoft Excel 2003," Comput. Statist. Data Anal. 49 (2005), no. 4, 1244--1252, available online at http://dx.doi.org/10.1016/j.csda.2004.06.016 but paywalled. I thought that this article, or a similar one, was recently discussed on HN, but I could not find an appropriate link.
On the other hand, I don't know anything about business. I can see an argument for using a widely-deployed piece of software for verifying R > E even if it is inappropriate for data analysis.