data based website design

We are a auto parts wholesaler who deal with more than 200 items with 15000 customer base. We are going to set up one website as the working station for all our sales staff. The following are the website about: 1. only the sales staff who has username and password can log in and use this website as working station. [login to view URL] the sales input the customer phone # and search, the website call bring the all shipping, credit history and contact information from the data base onto the screen. sale staff can correct the above information when they find the customer move or close the business. 3. once the sales staff close the deal, the websit can create the invoice, send the shipping information to our warehouse by email, make a note on our inventory list and delete the sale items from inventory. 4. after shipping the orders, website will save the new invoice under the customer new [login to view URL] we get the payment for this order, sales can increase or decrease the cusotmer credit level in credit history of this customer. [login to view URL] the owner of the website, can adjust the inventory of the items after we get the new shipment. the website must by secure and no sale or anyone can export the data base.