I can also block https by blocking port 443 that´s not the point. The point is to block "bad" 443 port traffic and let "good" traffic pass.I think that you can stop ALL https connections with squid.. if you want of course... but then, I dont know if there is such way as you described it. A very good ACL implementation is squidGuard.
But hey.. why do you want to stop skype?
Regards,
Edvin Seferovic