Create a function in Magento Onestepcheckout

We have a custom onestepcheckout page. Actually it is based on an onestepcheckout plugin, however we've customised it further to improve the interface & experience. We want to add 'email capturing' feature on the checkout page where the First Name, Last Name & Email of the customers should automatically get stored somewhere (database preffered) as soon as they enter these three details. Regardless of they proceed to enter their address or not, their details should get stored. Suppose if I enter my First Name, Last Name & Email, and then I plan to drop the cart, my details should get stored in the database. We need this feature to be implemented on Onestepcheckout - Address form.