This feature is designed for sellers which who deal in multiple currencies, such as buying products in Euros, but selling in Dollars or vice versa. A particular business may buy in Pound Sterling, sell to the USA, but usually trade and calculate profits in Euros:
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PC2 downloads live currency exchange rates a few times per day and will automatically and transparently bake these into all the formulas used in Excel, so that you can work with the foreign prices as supplied, but see profits in the currency that you understand on a daily basis.
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