125100 Rate Checker - UPS/USPS/Fedex

Greetings - I need a script, which will ask for the user to enter their zipcode, and the zipcode from where a product is being shipping from, and then script will contact USPS or UPS or Fedex, and return back the shipping cost. I need this to be in ajax - Preferably. I will be implementing this into another script that im currently using. Please do not reply: I can do this. If you can, thats nice for you. I want to know HOW you plan to do this, and your game plan to tackle this job. Thank you.