One data-heavy compromise would be to make a new filename each day, so that your users become accustomed to looking for a file in a certain directory having the most recent date in the filename; there would be dozens of other files that they skip past when they do this.

Another way is to instruct your users not to open the files at all, but to import the data into their own worksheets using one of the methods here, or simply to make cell references in their spreadsheets.