CarotDAV is multi protocol file transfer program supported by WebDAV, FTP, and other online storage services such as Box, GoogleDrive, etc.
It is quite simple and easy to use!
Using CarotDAV, you can easily download / upload files between local PC and cloud storage services.

To use Box, first you needs to make a "Connection Setting".
Click "Add Box" in the "Connection Setting List" form that appears,
enter the "Setting Name", authorize CarotDAV via Web, and click "OK".
After this, you can access your "Box" storage by clicking the "Connect" button.
Though you cannot open files directly, you can use drag-drop/copy-paste to upload and download files and folders.