Opening file, editing, save, exit, open, edited version opens?

If the document (Excel spreadsheet?) is inserted into a post/page, then that file is a ‘Media’ item, and the content is as it existed when you upload/inserted it.

If you want a dynamic document, then you could use something like DropBox or Google Drive to contain the file, giving permissions to anyone that has the link, and insert a link to that DropBox/Drive file. Then, any changes you make to the file (as stored in DropBox/Drive) will be available to visitors when they click on the link. They will have to have a Dropbox/Drive account though.

You might be able to FTP a new version of the file to the file/folder equivalent of the URL for the uploaded Media item. Haven’t tried this, but it should work.