Customise existing PHP script of invoice and billing

i have an php billing application already installed on server, want to make some minor changes in customer information form fields, and invoice billing options. i will explain everything graphically what exactly i want. you must have SKYPE, so we can discus about the customisation. their is no major programming , you just need to create some form fields in customer registration, tables in DB, and pull information from customer info to Invoice billing. My budget is max INR.3000/- **SERIOUS BIDDERS ONLY**