Sorry, I don't understand what is so strange about this; would you even want to type in a separate exchange rate for every single item in your expense report? Unless your trips last years or involved visits to Serbia during that one month when they had 14 quadrillion percent inflation, the exchange rate fluctuations are usually rather small. For example, if you go on a month-long trip to Europe and the euro strengthens from 0.855 to the dollar to 0.835 during that time, you would be looking at a hit (or gain!) of $20 for every $1000 you spend. But if you pick a median 'one rate' at 0.845, you'll come off at plus-minus zero.