To illustrate consider the following scenario:
Base Currency of the subsidiary is USD.
Report generation date = 8/8/2013
Exchange Rate for USD base to CAD foreign currency on the following dates:
8/1/2013 = 1.20
8/8/2013 = 1.22
8/31/2013 = 1.25
1. Navigate to Reports > Sales > Open Invoices
2. Set the As of field to Aug 2013.
3. Click on Customize to be redirected on the Report Builder.
4. Under Edit Columns, expand Open Invoices and expose the Current Exchange Rate field found under the first Currency subfolder.
5. Hit Preview.
***Result: The Current Exchange Rate column would show 1.22 for transactions denominated in CAD and 1.00 for transactions denominated in USD.