To override Reimbursable Amount for different currency purchase

Summary:

We have done the setup to allow users to select the reimbursement currency in expense report. However, user has to enter the foreign currency amount and exchange rate in order to derive the Reimbursable Amount in reimbursement currency. Is there a way for them to key in foreign currency amount and reimbursable amount directly into the system?

Content (please ensure you mask any confidential information):

Example:
Purchase an item USD: 302.29, credit card charged SGD 389.49
Submit an expense report with reimbursement currency: SGD
User has to enter USD 302.29,
(work out exchange rate 1.28846471930927 outside the system)
Input Conversion Rate: 1.28846471930927 in order to populate Reimbursable Amount of SGD 389.49.