National CineMedia, the in-theater advertising company that works with AMC Theatres, Cinemark and Regal for pre-show commercials content, has closed a major deal to venture outside of the cinema. The firm, led by Thomas Lesinski, has sealed an agreement to acquire Captivate Holdings, which powers tens of thousands of small screens in office buildings, lobbies and elevators that show short ads and content as people walk by (or when waiting for your floor in an elevator). The deal is valued at $275 million. National CineMedia already has a foothold in this business through all of its screens showing ads in movie theater lobbies (it had…