Meh. to add script either on mIRC write

/write (file name) then the line

if you want someone else to be able to add it

ON !:text:!addslap:#:{
if ($nick isreg $chan) { msg # sorry only Op'ed status can add slaps. }
if ($nick isop $chan) {
/write (file name) $2-
msg # $nick your slap message has been added
}
}

is personally what I use. Because this makes it so that if a non op'ed person tries to add one it alerts them that they can't. and doesn't add it. And only allows Op'ed people add them ;). Quiet a fun script.
and you don't necessarily need the message, but it is to let them know. (you can also switch # with $nick if you want it to send them a message.)

The Delete I don't know exactly because it would have to be the same phrase I think. Which if you want to remove them just go into the file and erase them.