In case anyone is interested, there's an Excel spreadsheet to calculate the Omega Ratio here: Omega Ratio in Excel.I prefer the Omega Ratio to other performance measures because it captures all the information in the empirical returns distribution, without place any assumptions on the data.

It's probably a few months too late, but here's a spreadsheet to calculate the modified Sharpe Ratio

I just came across this old thread, and I don't understand how that paper calculated the Omega Ratio either. Anyway, there's another method which uses the discrete returns data here: Omega Ratio in Excel