Simple database programming related work in excel

I want some functions to be added in the attached excel file. Currently, I have modified the file as such that when I type the Item Number, it fills the description and amount automatically. My knowledge is limited into this, so I want an expert to modify the file to add functions such as saving & viewing the invoices (vba code or other), auto showing the name list & price on typing a name, modification in the item code so that 1 item can be used only once. I will forward my clients messages. If you already have written codes or can search on the internet with correct keywords, then the work can be done easily by you in an hour..