The requirement is osCommerce based as follows:
Emails are sent to potential clients. These emails have a link to the osCommerce web site with a parameter identifying the particular email but not identifying the recipient of the email).
If a person clicks on the link in the email to go to the web site and then eventually makes an order this order needs to be recorded in the database (in a new table) along with the email identifier and the total value of the order.
The sending of the emails is not part of the project, just the code that will handle a link to the web site that has a parameter identifying the version of the email.
Any questions, please let me know.