usually only use one currency per account.
I haven't heard of any accounting packages that allow you to work in two currencies in one account. The reason is that currency exchange rates vary and sometimes very quickly.
If they didn't you could have a report multiply the currency in one account times a fixed amount or from a table to get any other currency.
But doing this you open a very sticky situation: the same report will be different tomorrow if you use up-to-date exchange rates. If you use the same amount for a month, say, then the amount in the end currency is wrong if the rates change and you're not using the changed rates.
Companies that consolidate data from plants in different countries will often use a rate that stays the same for a period, such as a month. They will take from one account in a local data warehouse or operational store, and consolidate to a centralized data warehouse (into a new account) at that rate.
So the answer is probably NO, you can't have two currencies in one account at same time. But you can create conversions based on an 'estimated' rate and use these for accounting for a period. Consult an accountant for best practices on rate conversion and consolidation.