550798 Mailchimp and oscommerce newsletter database sync 2

I have a oscommerce website. I need mailchimp api installed so that people can subscribe and unsubscribe with a tick box in their account page, also when they register. I already have the checkbox, at the moment these checkboxes are linked to osc newsletter database, but I want oscommerce database and mailchimp database in 100% sync without any importing or exporting. I also want to be able to send php mailer through osc, this part is already there, you just need to link the osc database to the mailer. please help me get this done. Thanks.