hmm just disable the default gateway, I have a set of batch files on my laptop to switch networks as it connects to quite a few different ones, see syntax below. Helps to rename your network connections something that is short and one word.
netsh int ip set address *name of connection* *static/dynamic* *if static fill the rest out* *ip* *subnet mask* *default gateway* 1
EG:
netsh int ip set address LAN static 10.0.0.4 255.255.255.0 10.0.0.10 1
netsh int ip set dns LAN static 10.0.0.8
so if yours is static you could do
netsh int ip set address LAN static 192.168.0.10 255.255.255.0 1.1.1.1 1
OR if if is dynamic you can still set the dns to an incorrect dns and it won't resolve anything...
That would stop internet connectivity, in a simple batch file.