Qsync access over WAN for different users

[Stefano1975]

Hi everyone,
In my NAS I created three users:
Admin (me)
User A
User B

I would like to allow user A to use his credentials to sync "shared folder A" via Qsync over the Internet, and the same should be allowed to user B (who should be able to sync "shared folder B").
Is there a way to do that without sharing the credentials of my QNAP account?

Thanks so much in advance.

Stefano