[Zubersoft]

If you go to Settings->Storage and uncheck "Let MobileSheets Manage my Files" and then you can find a way to import your files directly off the WD Cloud EX2 Ultra, then yes, you could have MobileSheetsPro look at that NAS for all the files. You'd never be able to use the app without a connection to the NAS though, so I'm not sure that's optimal (it depends upon your usage scenario). I'm guessing you can't mount that NAS in the Android file system though, so I doubt you will be able to get that to work. It's probably better to copy the files off the NAS on to the tablet itself, and then import them into MobileSheetsPro from there.

Mike