You can't do that directly as sshd only understands IP addresses. You may be able to knock something together using an openvpn up script
Shell command to run after successful TUN/TAP device open (pre
--user UID change). The up script is useful for specifying
route commands which route IP traffic destined for private
subnets which exist at the other end of the VPN connection into
See also the
--down option to clean up and the relevant parts of the documentation detailing script security etc.
You'll find the IP address of the tun device is passed to the script as an environment variable. Also sshd takes options on the command line of the form
Can be used to give options in the format used in the
configuration file. This is useful for specifying options for
which there is no separate command-line flag. For full details
of the options, and their values, see sshd_config(5)
So you could use
-o ListenAddress=<some address>
Presumably you have some out of band method of talking to your VPS so that when this breaks you can contact the server.