Sorry for the delay.
Here is a simplified example: http://dl.dropbox.com/u/18516025/excel_example.xlsx
. I think it's pretty self explanatory. In the first tab, there is a constant database of all the companies and their assigned numbers. There are going to be several months (2nd and 3rd tabs are just for an example). I explained everything else in the first post.
Could you do a concrete example of my case and upload is somewhere, so I can take a closer look at it? Thanks in advance.