Make a feed URL via FTP and upload a new file version without link changing

Fix budget 10 usd I have a csv data feed. For a price comparasion site I have to upload this file to my site via FTP and send the feed url link to price comparasion site. They will download the csv 2 times a day and upload the products to their site. But sometime I will update my csv table manually. It means I have to change the table and upload again but the link can not change because if the link change the price comparation site can not download it. Do yo have any idea for it? Thank you