At 11:15 central time, the pilot of a Cessna 172L lost control on takeoff and struck a runway end identifier light control box. The pilot was not injured. The pilot said his seat slid back as he was trying to attach a GPS to his leg during the takeoff run. The airplane went off the left side of the runway and struck the box. The pilot aborted the takeoff, then departed in the airplane and flew to Kenosha.