How do I calculate the IRR and ERR like Lotus 123 2.0 used to calculate and foreign banks use?

IRR is the International Rate of Return and ERR is the Economic Rate of Return. Lotus 123 2.0 used to be able to calculate this, but modern spreadsheets don't calculate it anymore.





Foreign banks have old data in Lotus 123 WK1 format, and hardly anyone has a copy of Lotus 123 2.0 for MS-DOS or OS/2 anymore.





Anyone know how to calculate it? I used to know but I forgot and lost a link to a web site that said how to do it.

How do I calculate the IRR and ERR like Lotus 123 2.0 used to calculate and foreign banks use?
Excel and Financial Calculators(example: HP 10B calculator) have an IRR function, but it's the 'Internal Rate of Return' and not International rate of return.





Also, the ERR and IRR are the same thing.





Edit: I've never heard of it combined into one theory... but I suppose we always learn things. I do know that you always consider the exchange rates when considering foreign investments(Interest Rate Parity).





Anyways... this website is probably what you're looking for: http://internationalecon.com/Finance/Fch... . The thing is that it can't be a direct formula considering you have to know the expected future exchange rates(Forward Rates for the 2 currencies). You could create an excel sheet and use a row of boxes for you to insert the forward or future rate of the various currencies. Unless you're doing the calculations 'Post Facto'.





As far as the economic rate of return... I would like to see the differences as well. I do know that an economic profit, is the profit above and beyond the expected normal profit. The economic profit will be zero when there is perfect competition, because profit should equal costs(which in economics includes opportunity costs of investing somewhere else). So, it is possible that someone may calculate an economic rate of return based on combining these 2 concepts as well, whereas Internal Rate of Return would be an actual Rate of Return without taking into consideration the 'Economic Normal Profit'.