Hi,
Having 15+ years in computer applications, programming, databases, networks, and various operating systems this does seem like a very simple task.
If you have access to Microsoft excel, it has a built-in function that will do this for you.
I will be able to provide you with step-by-step instructions on how to do this or I can create a little how-to video for you, or if you want I can even walk you through the process via phone/skype/facebook-chat.
The duration of this task should be just couple of minutes; even in worst-case-scenario less than 1hr.
Sukhi