“Is this The Box?” asked Buckingham Capital chairman Larry Leeds as he hopped out of his Mercedes to attend Julie Macklowe’s 35th birthday party Saturday night at — The Box. Jason Wu, Chris Benz, Yigal Azrouel, Veronica Webb, Ann Dexter Jones, Tom Florio and Macklowe’s husband, Billy Macklowe, were inside the downtown nightclub, celebrating both Julie’s birthday and the launch of her beauty company, vbeauté. Sean Paul performed songs from his upcoming album, “Tomahawk Technique,” while Julie, clad in thigh-high leather boots and a short, rocker blond pixie cut, reflected on her dorkier days during a speech. “I was actually in a marching band growing up, and I played the trombone,” she joked.