For your own protection, I would recommend picking a specific channel or channels where you're going to be doing this. Let me know if you'd be interested in a version that would only trigger if you were opped on the channel.

This code will put a ten second delay between each use.

Code:
on 1:text:hi:#:{
if ((%wait.ctime !isnum) || ((%wait.ctime isnum) && (%wait.ctime < $ctime))) {
/msg $chan Hi $nick
set %wait.ctime $calc($ctime + 10)
}
}