Ariba / Zencart Bridge

We need a freelancer who can program a bridge between our Zen Cart Store and the Ariba Purchasing System. We have support with Ariba and have received documentation that should help with setting up the connection. Workflow: Customer would log into the Ariba system. Within Ariba there will be a link to our store. Clicking on the link sends them to our site, using cXML to authenticate with Zen-cart. So the customer would not need to re-login to our store. Next they use Zen-cart to find and add products to their cart. When they go to checkout we would need the store send them back to Ariba with the product and price information to pay and finish the order. We would also like to be able to track users that have checked out Zen-cart. So we know how many orders to expect. You will need Knowledge of the following: Zen-cart PHP / CSS cXML MySQL Experience with Ariba would be a plus.