I have a server: serverA.maindomain.com

and another serverB.maindomain.com

The DNS records for maindomain.com are on serverA

so the serverB A record is on serverA which is fine (i am aware it's a risk if serverA goes down).

If I'm setting a sub domain of serverB such as site1.serverB.maindomain.com I have to setup an A record on serverA for the subdomain and I don't want to have to do this every time.

Is there anyway I can setup a wildcard A record for subdomains such as:

Thanks in advance, and apologies if this makes little sense, I don't think I've explained it in the best way.