Exchange Rate Calculator - does not fetch from Currency Exchange?

Dear .


I made a child table and named it a calculator.

i want when i select US in the field currency So the Filed Exchange Rate

fetch its data from The Currency Echanger
so in this example it suppuse to be 8

i attempted this script

cur_frm.add_fetch(“Currency Exchange”, “exchange_rate”, “exchange_rate”);

and i made the Currency filed Type Link option Currency Exchange
so when i select it gives me
it suppose when i select one of them to fetch the filed exchange_rate from it to my Calculator exchange_rate

But it didnt

By the way i successfuly fetch using this method in employee

cur_frm.add_fetch(“employee”, “employee_name”, “employee_name”);

But i was fetching in parent DOCTYPE
But here i am trying to fetch To a Child Table

waiting your suggessions dears .

thanks a lot for your help

Cool! You have looked around some for eg Currency Exchange rate auto