Average exchange rate based on other exchange rate

Is there any functionality, where SAP calculates FX rate for Particulate rate type based on other Rate type?

Ex: we have M rates which are entered on daily basis from external financial co., so for given month it will enter different rate for 30 days.

now at the end of the month we have Average rate type A (which is used for B/S closing activity), which is nothing but an average of 30 days rate of M Exchange rate type.

So we wanted to have SAP calculate Rates for Rate type A automatically based on M rate, is there a standard config for such process.