What is wrong with this formula? CASE WHEN {currency} = 'US Dollar' THEN {fxamount}*0.85 ELSE {fxamount} END

{currency} = ‘USA’

The text will have to match what is set in your account Currencies. What error is your original formula ?

We're using US Dollar. Invalid Expression....

I cut and paste that into a Sales order search as a Formula (Numeric) and it's working.

Try using

{currency.symbol} = 'USD'

The problem with the currency name is that it can be changed, but the symbol will always be the 3 character ISO currency code.

It's working now as well on my end.