Worldpay oscommerce contribution fix

Contribution can be found here: [login to view URL],882/download,5291 There is a problem with call back faeture in this contribution. If you cancel a payment, you are redirected back to the store to either chose another payment method or try again. The callback feature returns you to a checkout called in http and not https. I need someone to fix this so it is called in http. This should be easy job for someone, one file to work on.