Paypal and KNET (kuwait payment gateway)

hello I need to make small program to send invoices to my customer via email with 2 link one to pay with knet and other to pay with PayPal I need it to be sample: in my end: can change the email from address so I can use it for 2 or more of my services can enter customer email and name and invoice subject line invoice details line invoice amount ( us$ or KWD ) (can add one currency and auto calculate the other one ) see a list of invoices that I sent in a table and see if its paid or not and when click on invoice number can see the details and has the option to resend the invoice customer get an email: with invoice subject as email subject see invoice details with option to pay by clicking on one of 2 links to pay with PayPal or knet