Currency Translation based on Last Day of the Acquistion month

Dear all,

Request to help me in understanding how we can calculate the currency translation rate as per the last day if the acquistion month..

For Example if the Acquistion date : 01/01/2008 (mm/dd/yyyy) the currency translation should happend based on the rate maintained as on 31/01/2008.

Thanks

Pavan Kumar Prakhya