[AccessD] Multiple Currency types

I have a field that is used to retain the historical cost of an item and up
to now is has all been in US dollars. Just got one in UK pounds. There's
more coming up too.
 
I've never dealt with multiple currency types before. How do you suggest I
store different currencies in my table? Do I need one column for amount and
one for type of currency or is there a way to do this with formatting,
masks, etc.