I'm using the template you can download from office online desktop services template, which basically gives me an invoice system. In the total amounts at the bottom when it brings up as $ sign when all I need it to be is a £ sign.
Where are you trying to do this? Form, report, query, table? If table, open in design view and make sure data type is currency. Go to general tab select "Euro" under format. See attached image.
I think you are better if you are using more than one currency to store values and their Currency and cross-reference to a Currency file or allow dynamic Exchnage Rate and store this rate or a combination of the two. You can have a feild denoted as cuurency for differing currencies as currency only looks at the (global) regional settings.