Zen-Cart custom shipping module

I have an online store running Zen-Cart. We use a shipping broker that gets us good rates on many of the major courier companies. The shipping broker has their own system for preparing the shipments and selecting the courier/method. Thus far, we have been using per-item calculation for shipping rates. Of course, for customers close to our location, the shipping rates are higher than our cost. For those far away, the rates are sometimes a little lower than our cost. The shipping broker has just release a XML-based API to their system for quote generation. I need a module to pass weight, city/provide/country, postal code and value to the API using XML and return rates based on different couriers/methods. In addition, the modile should allow overriding the names of the different shipping methods (which are also numbered in the API), allowing/disallowing specific shipping methods (again, by number), and allowing percentage and/or amount markup of the weight and/or cost.