Uploading multiple records

Hi to all.
I’m working on a B2B shopping portal.My problem is how do I upload data(could be thousands of products)of my prospective customers(businessmen) to my database.

Currently we take product info from registered businessmen manually(they submit their product info on paper) and add it to our database manually.

I want a way secure way through which businessmen could upload hundreds of records at a time to my database through the web site.
Thank you.