I don't understand what you mean by a "quiet ban".
A ban prevents a person from joining a specific channel.
If you don't want to see the ban command you can prefix it with a . rather than the / which will make the command silent
eg: .ban -k #chan $nick
vs.: /ban -k #chan $nick

If that's what you mean, then you can use
Code:
 .ban -ku300 $chan $nick
This will kick and ban the person for 5 minutes.

If this isn't what you mean, then please clarify.