Urgent : Ubuntu should automatically add dynamic dns record after VPN is up

Ubuntu 18 automatically connects to OpenVPN on booting and also later (whenever internet gets restored). It gets a different IP every time on VPN interface hence you need you need to add its hostname and vpn interface IP address to the dynamic DNS server as an "A" record with a very short ttl (or keep alive every few seconds) - so only valid DNS records are present. You also need to delete the old invalid A record of this host (if present)

DNS server is running on Windows Server with non-secure updates enabled.

I am able to achieve the goal by executing nsupdate command manually. You need to automate it. I am open for any other method.

Looking only for experienced freelancers who can help immediately.