Something

void World::SendInstanceMessage(WorldPacket *packet, uint32 instanceid, WorldSession *self)
{
	m_sessionlock.AcquireReadLock();

	SessionMap::iterator itr;
	for (itr = m_sessions.begin(); itr != m_sessions.end(); itr++)
	{
		if (itr->second->GetPlayer() &&
			itr->second->GetPlayer()->IsInWorld()
			&& itr->second != self)  // dont send to self!
		{
			if (itr->second->GetPlayer()->GetInstanceID() == instanceid)
				itr->second->SendPacket(packet);
		}
	}

	m_sessionlock.ReleaseReadLock();
}