Need to edit a javascript Ajax CI code in a module

Hello, Firstly this is a job for experts. small work but not for ametures. Srong knowladge on Ajax , javascript and CI is needed. need the job to be doe very [login to view URL] an expert its maybe a 1 hr job. I have one CI web app running. I have a Point of sales running. I want to add the product wise tax in POS. previously the POS had a Fixed tax rate for all . now i want to add Product wise tax rate. Tax is added in db and product module. Now In pos You have to add the tax dynimacally from db. Again telling its not a job for ametures. but ofr expert its 1 hr job max. No payment before the job finished. and acceptence who will offer more that 1 day to finish it.. For more we can chat.. Thanks