NT SMB connectivity

OK, guys and gals,
I am trying to “block” access to a NT 4 server through the INTERNET. I don’t want anybody to be able to get to or connect to the default system shares, such as \\servername\c$, etc… I am blocking ports tcp and udp 135-139 on the router, but I can still get to those shares. What am I missing? Is there more ports to be blocked ?
Thanks,
D
P.S. turning off the server service is not going to work; the server is dual-homed and I need access from the “other” side.