Magento project - custom module

URGENT!!! Extensions i'm using are: - onepagecheckout - Australia Post eParcel extension Basically, what is need is .... The csv data that is used to calculate shipping in checkout (from Australia Post eParcel extension) must be shared to calculate shipping in: - product details (instead of customer choosing state, they will have to enter their postcode) - shopping cart (we will add a postcode field which is compulsory for customers to enter to calculate their postage cost) So basically, everything will be just based on weight/postcode. Tell me if this is okay here is the australia post eparcel extension [login to view URL] PMB me for more details and our website