116144 Shopping cart customization

This project is for what I'd imagine to be a fairly small amendment. Currently my website "[login to view URL]" has a shopping cart installed (mofcart)and finishes up with a submit form, with all values stored as hidden. The submit button then submits these values to protx for processing (I'm still using their simulator at present). I require a number of these values to be encrypted using XOR encryption (3 of the values must remain unencrypted however) prior to being sent to protx. I'm not sure whether it's easier to customise the current code or to write a go between script, so that the shopping cart submits the values to the new script which does the encryption and then autosubmits the encrypted string to protx. I will advise the specific details of protx's requirements to the winning bidder.