Different primary email addresses for invoicing/statements

Within the customer area it would be useful to be able to record an email address for invoicing and a separate email address for sending statements which automatically inserts into the email template. Currently, i can only record one primary email address which pops up for every email. Most of our customers have a seperate email address for invoicing and statements.  It is very time consuming to go into each customer and find a different address for emailing statements as the invoicing email pops up as it is the primary email.