Hello,
Without knowing at this point what sites & data you need to fetch from, I can say that I've a fairly solid grounding in this kind of task. Apart from my day to day work, building php and python applications, in my spare time I build bots to extract planning applications from local government sites.
Will you be running this as part of an existing application? I'm happy to build it in whatever format you require, but if there's flexibility on choice of language, I've built up considerable support libraries in Python, so I imagine I'd be able to deliver much faster using those. Of course, this depends on what constraints you're operating under, and I'm happy to accommodate as necessary.
As a rough plan, I've added 2 deliverable milestones as suggestions. I'm open to changing this around if you have a different view:
1. Main application, extracting data from the sites you require, and
2. Ensuring the data produced is in the correct format, according to the master key you mentioned, and easily read by excel
I'd really like to hear more details on what you need, feel free to contact me if you think I can help you out.