Sending template email to secondary email address

[HappyHippo]

Hi experts,
I want to send order confirmation email and other template emails to user but on her secondary email address not the primary one. I have stored secondary email to customer's custom field.

sendTemplateEmailToCustomer1  and  sendOrderConfirmationEmail1  uses customerId and session id respectively. I believe these methods use "customers_email_address" field to send email. 

Is there any way i could send template email to customer's custom email address? (Can not use BCC as in EmailOptionIf , Has to be 'TO' address)

Thanks a lot.