Software to collect information

I need you to develop some software for me.
I would like something to collect some information from a website and after to compare the information and to show the difference between 2 different days .
This software must to be able to collect the informations form 50 websites. All websites are different structured, must be something customizable for every website.
Another thing I will want to include in the same software is to be able to add or upload files that contain other informations about the products information we collected previously.
Can be use any programming language or technology you think it’s easy and fast .

I will can explain more in private. I will select a freelancer just after a Sample to see if he or she understand what I need .