If the company's system currency forms part of the EU's monetary union - EMU - then you can convert the currencies via the Euro. By selecting this setting, the new currency will be entered in relation to the Euro instead of what its rate is in relation to the system currency. Please note that the Euro currency (EUR) must be entered in relation to the system currency. Therefore you should not check this setting for the Euro currency.
Please Note! This setting should never be entered if your system currency is not included in the EMU, i.e. if your system currency is SEK. As long as Sweden is not participating in the European Monetary Union (EMU), all foreign exchange rates should be entered against the SEK. Under the System tab in the Settings procedure, you will find a setting called Company currency part of EMU's monetary union?.