Database for Printing Simple Invoices

We currently use handwritten dockets at the point of delivery of our products but need to change to printed dockets. We need a simple database tool that will run on Windows XP that will allow our driver to select the customer name from a list, automatically populate the address and store number field, assign a unique document number, choose up to 50 possible products for delivery (and quantities of) and produce either a delivery docket with just quantities or an invoice that includes prices. Two copies are printed and one is our proof of delivery. The information that is printed out needs to be recorded in the database against the document number. Every couple of weeks the information needs to be put on a usb drive and brought in to the office. We have five vans that need this database, and the office computer will need to be able to centralise the data so that it can be transferred (punched) to the office accounting system (Sage 50). For those who might be able to help I can provide samples of invoices, dockets, customer lists, product lists all in Excel. We're a small business so we cannot afford to get this wrong. Thanks for reading.