Auto Update from Spreadsheets

Hey guys putting a pricelist on my website have a few different wholesalers that I buy from, and I want to be able to everyday update the prices and then if someone says they want to buy that product I have a way of checking where the source is.

I get the wholesale lists in my email and I download them to a folder in my computer i then want to be able to preform a check that will put the cheapest prices on the site, plus like 30% or something like that. Can anyone tell me the best way to do this, not to sure if it can be done through HTML or if I have do it some other way.

Thanks for your help

Jason