conditionally executing 2nd command

hello

i want to write a windows batch file so that system first checks if preferred DNS server is set (exist) in NIC IPV4 settings, system continues executing the next command (which isnetdom join localhost /domain:......) 

but if it isn't set, system runs first command (netsh interface ipv4 set DNS server NIC 192.168.1.1 validate=no)

what would be that script?  ( i think via "IF" we can do that)

is this right forum to ask this question?

thanks