Sounds to me like a theme.
A theme uses a text event and echo;s the text on your screen how you want it and halts mIRC from showing its normal message and duplicating it.
So they use ...
echo -t $chan $nick : $1-
So make the # the channel name and it will only perform in that channel. And yes, it could conflict with another theme you may have. You could make sure the script file is first in the list to help that.