CS-Cart - Special invoice number addon

We need special invoice numbers on invoices in CS-Cart. Normally cs-cart gives invoices a number like #1, #2, #3, etc... I want every year a new range, for example : GB20120001, GB20120002, etc Next year automatically : INV20130001, INV20130002, etc... We want a full manual how to change it in CS-CART so we can do it by our selves. So you have to give instructions like : - open file with filename "filename" - Search for text "text-code" - Replace by text : "new text-code" Also MySQL changes must be in manual. We want 2 variables set in config-file : - Prefix, like INV in example. - Number of positions after year-stamp. So, when admin put this on 6, you get : [prefix][year]000001 as first of the year. If you put this on 4, you got : [prefix][year]0001 This number must replace order_id in all invoices. (Printed invoice by admin, but also email-invoices to clients) We want the full copyrights of this changes. We will pay only after finish project with 100% satisfaction. We want invoice of your company after finishing the project.