You can assign one currency for each customer or vendor so you'll create new customers or vendors to use in your foreign transactions.
All existing customers and vendors will be assigned your home currency when you turn on multicurrency. The currency can't be changed for names that already have transactions recorded against them.
Use the Customer and Vendor Centers to create foreign customers or vendors. If a name is already listed using your home currency, assign a slightly different name to the foreign customer or vendor that you create.
Continue to use these home currency customers or vendors as you close open balances. You'll use your foreign customers or vendors for any new sales or purchases you create but you'll continue to use the home currency names until you complete any current open transactions.
and employees can't be assigned a foreign currency and are always in your home currency.