You can use a script like this to do such a thing:
on 1:INPUT:#channelnamehere:{
if ( %locked == 1 ) {
if ( $$?="This channel is locked, enter your password" != password ) {
echo -a Invalid password entered
halt
}
set %locked 0
echo -a Channel unlocked
}
}
Using that if you typed
whenever you left noone would be able to message #channelnamehere until the word "password" was entered into the edit box that would pop up if they tried.
Having said that it would be a ncie feature.