Oscommerce contribution customising

We have installed the following contribution on a oscommerce website:- [login to view URL],2082/category,all/search,referral This contribution has been modified slightly so that instead of someone manually entering a "referral" code it appears in a drop down list of Charities to receive donations. What we need done is some minor fine tuning to the coding so it does the following:- 1) When a new customer registers they do NOT automatically get a referral code of their own, but a referral code is rather set manually in admin (admin sets the Charities eligible to recieve referral points) 2) When a purchase is made and the drop down is selected the referral points get allocated to the selected Charity. 3) Selected Charity to appear in checkout, confirmation emails, and order section in admin.