US exchange rate in reports

SOLVED

Hi, 

Can someone explain how do I make a monthly entry to adjust the US exchange rate in order to have the right information in the reports. I already use the exchange in each invoices, but I would like to adjust, monthly, with the Canadian Bank monthly rate in order to have the right information showing in the reports.

In the balance of verification my US account + my exchange account should equal the monthly rate X the balance of my bank statement but it doesn't seems to work Disappointed  The previous month changes the current month ... There is a detail that I don't get!

Thanks in advance,

Melanie