OS Commerce quickie - make email link https

We need to change the "detailed invoice' link that is in the emails sent to a customer when the status of an order is updated, from http to https? we do not use a secure cart but need the link to the [login to view URL] page to be secure I simply need someone familiar with OS Commerce / Creloaded to advise the tweak that needs to happen, we will do it ourselves - will pay $10US to the first person that advises!!