The simpliest way for one command - is just put to it in checking of vcmp.command2 signals. Just add before the string
else vcmp.msg %id Error - Invalid System Command $+ , Type "!commands" for a list of commands!
The code for checking say command:
elseif ($2 == say) {
if ($vcmp.cmdcheck(!say,%id) == fail) !halt
elseif (!$3) vcmp.msg %id Error - Missing Information, $2 <text>
else {
var %a = 0
while (%a <= 50) {
if ($vcmp.name(%a) != Unknown) {
vcmp.announce %a $3-
}
!inc %a
}
}
}
Good luck!