currency differences for partial payments

Dear experts,

I have done customization of currency differences for partial payments

SPRO ->Financial Accounting (New) ->Financial Accounting Global Settings (New) ->Global Parameters for Company Code->Currencies ->Indicate Currency Differences for Partial Payments.

but still after this configuration system dose not calculate currency difference and partial payment can be posted without exchange rate gain/loss.

Any suggestions would be appreciate.

Best Regards,