Hi Zura,

The journal entries created after validation or invoices or sales or purchase.

You need to trace which method is made impact to update currency rate entries on income and expense account.

Like, in Accound module inside the bank statement.

Path : addons>>account>>account_bank_statement.py : line no: 682

You will find one method with name get_currency_rate_line  which is used to create accounting move for create entries on gain and loss account by overriding this method you can change with currency rate of yours instead of getting base rate, you can apply your current/or calculated rate.

Or you may find any other method inside account module which have the same behavior while any entries being generated.  you just need to override that method which will solve your problem.

Hope this would help you.

Rgds,

Anil.