host/de-host? Your host is normally your internet provider, so you can't de-host someone, since, in theory, the process of de-hosting someone would remove their internet provider.
Do you mean op/deop, half-op/de-half-op, voice/devoice?
Note that the message is set up to be displayed only when the person joins the channel, not when a person has their status changed. Based on the script given
here