To enable advanced currency management:
Enable multiple currencies for your organization. For more information, see Managing Multiple Currencies.
Click Your Name | Setup | Company Profile | Manage Currencies.
Click Enable.
When prompted, select Yes, I want to enable Advanced Currency Management and click Enable.
When advanced currency management is first enabled, your existing exchange rates automatically become the first set of dated exchange rates. These rates will be valid for all time, until you define another set of exchange rates.
To disable advanced currency management:
Click Your Name | Setup | Company Profile | Manage Currencies.
Click Disable.
When prompted, select Yes, I want to disable Advanced Currency Management and click Disable.
If you disable advanced currency management, all currency conversions will use the static conversion rate. See Editing Conversion Rates.
When advanced currency management is enabled, Visualforce and components cannot display currency fields.
Cheers!!