Something

on *:JOIN:#:{ 
if (%agon == true) notice $nick Hi there, welcome to $chan !! 
}

on *:text:autogreet*:*:{ 
if ($nick == tysonfawlay) {
// checks to see if the nick is you

if ($2 == off) {
// checks to see if the second word is "off"
set %agon false 
// sets the variable %agon to false
notice $nick The auto-greet is now switched OFF 
}

if ($2 == on) {
set %agon true 
notice $nick The auto-greet is now switched ON 
}

}
}