Help with a simple scritp

Hey can someone help me a simple script that when someone sit in determined prim whisper a messange to the avatar

Here ya go..

default
{
state_entry()
{
// or whereever you want the person to sit vs the prim
llSitTarget(<0.0, 0.0, 0.1>, ZERO_ROTATION);
}

changed (integer mask)
{
if (mask & CHANGED_LINK)
{
key sitter = llAvatarOnSitTarget();
if (sitter != NULL_KEY)
{
llInstantMessage(sitter, "stop sitting on me, Mr Big Butt!!";

// throw them off!
llUnSit(sitter);
}
}
}
}

=D thx for the help