type /help /ban for more info
also /help $mask
/ban [-kruN] [#channel] <nickname|address> [type]
Bans someone from the current channel using their address. To do this, it first does a /userhost on the user, which gives it the user's address, and then it does a /mode # +b <user address>.
If you specify the -k switch, mIRC performs a ban/kick combination on the nickname.
If you specify the -uN switch, mIRC pauses N seconds before removing the ban.
to ban and kick with an auto unban
/ban -ku300 $nick (reason is optional)
the -k again means kick them too
the u means unban them in N seconds
/ban -ku300 $nick 3 You were warned.
you would see the ban
*!username@*.host.com
then the nick would be kicked with the reason "you were warned"
5 minutes later (300 seconds) the ban would be lifted