Is it possible to connect a form to an Excel spreadsheet on Google Drive, One Drive or Dropbox so that each time it's filled out on the device it will add a line to the same spreadsheet?
When you create new versions of your form, we append rows to the same worksheet, just adding missing columns as needed.
We currently don't support appending rows for the Excel side on Dropbox, Google Drive etc. If we did, we would have to download the file each time in order to append the row, then upload it back to the storage location. When there are many entries coming in, and often concurrently, this becomes very problematic.
Google Spreadsheet doesn't encounter this problem, because we are able to add rows through a programming interface (called an API) instead of downloading the spreadsheet each time. Microsoft is said to be launching new APIs in the future that will match Google Spreadsheet. When/if this happens we will look to add appending support for One Drive and Office 365.