FOREX TRANSACTION: IT'S ALL IN THE EXCHANGE If you've ever traveled overseas, you've made a forex transaction. Take a trip to France and you convert your dollars into euros. When you do this, the exchange rate between the two currencies—based on supply and demand-determines how many euros you get for your dollars. And the exchange rate fluctuates continuously. A single dollar on Monday could get you .70 euros. On Tuesday, .69 euros.