I need invoice currency to be different than the products currency

[andika]

I need invoice currency to be different to the products currency. So main site shows usd currency prices but I need generated invoices to be in other currency I added to 'Additional Currencies'. How can I do that ? I see many providers do so with WHMCS , must be a simple way I just can't figure it out. I know there is 'more option' on each client invoice that can do that but only after invoice ists already generated, I need  all invoices to be generated in my 'additional currency'.