It wasn't the voice that drew Lex's attention away from his thoughts. It was the sight of his expensive wooden door soaring across the room and partially damaging the wall on the other side of the room. Chin lifting upward, Lex stared off at the intruder. One hand instantly slid it's way underneath his desk, fingers pressing down against the alarm button that would soon send security rushing into the room. That was, if there was any security left to actually help him at the moment.
"I'm guessing that knocking isn't a formality in Krypton," Lex commented. "Nor is respecting the property of other people." That said, the Luthor rose from his chair and stepped around his desk. There was a small box resting just along the far edge. In that box? There was a healthy portion of kryptonite. If he could get at it quickly enough, then Jor-El would hardly be what Lex could call a problem.