I need to import sales data into Microsoft Navision

We receive sales data weekly in one csv file for our products from a customer for each of their stores. This file on each line has the following : -

Date of Transaction, Store ILN Number, Product EAN Code, Qty, Price, Stock Level

We will create an excel template that converts the ILN Number to the Customer Account Number in Navision, and the EAN code into the product code on Navision.

We would like you to help us setup a procedure and provide the technical know how to import that file into Navision, and have it create an invoice on each customers account based on the products for that store in the week. (So each store could have one invoice per week with a line for each product they sold that week), and then create a single credit note for the same products on one single 'head office' account, that offsets all the store invoices. In addition the invoices will need to be imported using the pricing for each product code setup in Navision.

A user guide would need to be provided to show the end user the procedure they would need to follow each week to import the excel file.

Please post a question if you require clarification on any of this!

Note that Software version is :-

Microsoft Dynamics NAV 2009 R2
Version DE 3.70