How to derive conversion date based on the Journal Accounting Date for Journal Approval Rule

Summary

My requirement is to derive conversion rate for the previous year's last month, month end rate for journal approval rule.

Content

My requirement is to derive conversion rate for the previous year's last month, 'month end rate'. Previous year to be calculated based on the accounting date of the journal. This conversion date would be fed in the journal approval template below in place of date.

Journal Header.Running Total Accounted Credit.doubleValue()*CurrencyConversion.getRate(Journal Header.Entered Currency,"USD",Journal Header.Accounting Date,"Corporate",0)