Due Date on Invoices

Should be able to amend the due date on sales invoices per each specific invoice. At the moment have to amend the payment terms days on the customer account then change it back once I have created the invoice. For example,If I wanted to send an invoice payable in 7 days, I should be able to just select this when creating that invoice not change my whole customers payment days from 30 to 7, then remember to change them back once complete. Thanks :)