Customize Zen Cart shipping/checkout module

1. Calculated shipping based off origin address, destination address, dimensions and weight of package. 2. Option needs to be present for providing different origin zip for particular products (note that we sell some laptops that ship from Albany, OR at the UPS Store we have contracted and we sell other laptops that ship from our location in VA. 3. Domestic Shipping will automatically add $3 for signature cost and $0.55 per $100 of item value for insurance. Domestic Shipping methods will include UPS Ground, UPS 3 Day Select, UPS 2 Day Air, UPS Next Day Air Saver, UPS Next Day Air, and UPS Next Day Air AM. I want to give discount of 30% for 3 Day Select and Air methods. 4. International Shipping will automatically add $3 for signature cost and $0.55 per $100 of item value for insurance. International shipping method will be UPS Worldwide Saver Express (no exceptions). I want to give discount of 50% for international shipping. In short, shipping is calculated as follows where I = Insurance cost, S = Signature cost, RR = Retail Rate for UPS shipping and D = Discount provided. Shipping Charged to Customer = RR * (1-D) + S + I (retail rate less discount plus signature + insurance) RR (retail rate) is provided by UPS shipping calculator based on the package weight, dimensions, ship from location and ship to location. It is small [login to view URL] need to modify/create php code implement in any website you choose and inform me. I would pay after seeing it by paypal.