In my new position I'm frequently needing to compare different versions of the same excel file (the FRAM model uses excel for inputs and outputs; I frequently need to compare the inputs or outputs of different model runs). Does anyone know of a good non-browser tool for comparing excel files? Basically looking for a `diff` analog. I'm tempted to write an #Rstats package for this, but if it exists I'd rather not re-invent the wheel.