I want to be able to link a spreadsheet to a card that it relates to while the file is on DropBox and have it update on Trello automatically so I don't have to re-upload it every time a change is made
Trello – link files on DropBox onto a Trello card for members to see and so it updates when the file is changed
dropboxtrello
Best Answer
Instead of attaching the file, you could use the Dropbox link feature. The resulting hyperlink would take the Trello member to a preview of the file with a download option. It is always the most recent version of the linked file.