Invoice manager for Wordpress site

Hey! I need someone who can encode and implement a user database for our wordpress site. We want to use an existing script with some modifications have a look! [login to view URL] We want the user to be able to fill in a web form which then comes out as an invoice. The user should be able to save his invoices on the page. We also want a calculator where you can select the country (5 countries) and automatically get tax data calculated on what sum the user enters. Instead of admin sends invoices to clients we want it the other way client does job for customer ----> client generate invoice ----> client sends invoice to us (admin) what we need: CLIENT Client login screen personal page with customernumber, adress, contact, bankaccount etc also available for us (admin) iNVOICE GENERATOR tax calculator depending on country ability to pdf or view directly in web browser, and auto send mail when invoice is done add new customer info and save for invoices ability to refer new clients and get bonus points (referal link) Admin Ability to view and edit clients invoices, "approve them as finished" (when approved the client should se a mark or something next to the invoice at their view) Ability to sort clients list name, latest invoices etc ability to pdf or view directly in web browser, and auto send mail when invoice is done