This is not answering your question but it is an alternative to fixing your problem.
You can use the Easy Digital Downloadsplugin. You can use that to sell your excels sheets.
This plugin is free although add-ons cost extra.
One alternative that I know of is Google Drive. First of all upload the files and then click on the share button on top.
This will give you a link which is of the form
Make a note of the FILE_ID.
On your website, create the following link.
The setup for this can be fairly complex, but a good place to start is to use a "multiple package" plugin... such as Packages Configuration for Woocoomerce or Multiple Packages for WooCommerce, which allow you to split the packages up for each vendor. This way, customers can choose a shipping method for each package on the Cart page.
Allowing the vendors to ...