WorldPay Integration Into OScommerce Website

I have an OScommerce website with WorldPay installed, but there is a problem. I can't figure out how to create a response page that will return customers back to my website after they have paid and then log the order in the backend admin of our website. At the moment when a customer click 'Pay Now' on our website it logs the order in our admin and redirects them to WorldPay. Then after their payment has been made, the customer stays on the WorldPay page. This is bad because the order gets logged in our backend admin BEFORE they have made a successful admin. So if their payment is declined by WorldPay or they leave the WorldPay page before completing payment, their order is still in our system and there's no way of telling if they have made a successful payment without checking our WorldPay account as well. This takes up a lot of valuable time and resources having to check every order. This is how we want the system to work: 1. Customer buys a product from our website. 2. They enter their details and click 'Pay Now'. 3. the customer is redirected to WorldPay. 4. They enter their payment information and their payment is successful. 5. After the successful payment the customer is redirected back to our site and their order is logged in our admin. We need this completing urgently.