historical consolidation rates

We are trying to consolidate a reporting entity whose accounting (functional) currency is than the parent node whose accounting currency is USD. We are not able to get the Historical Consolidation Rates to work on certain general ledger accounts we wish to translate at a historical exchange rate rather than the current month rate.

We have populated the Historical Consolidation Rates page with the entity and account and historical amounts both in USD and the sub-node currency. We have chosen the option "Keep Balances Separated by Reporting Entity" for this account.  Are there other settings we need to engage in order for this to feature to work ? 

Thanks in advance for any assistance