I don't believe it is possible to change the currency of the Expense Report to one other than that specified in the employee record. We have the same issue but as we use OpenAir we were able to rollout a custom solution that will import the Employee expense report into NetSuite as a vendor bill and therefore in any currency we want. The solution on SuiteAnswers for NetSuite isn't great https://netsuite.custhelp.com/app/answers/detail/a_id/42248/kw/Expense%20Report%20currenc