ROBSON WALTON, 10% Owner at Walmart (NYSE:WMT), executed a substantial insider sell on September 10, according to an SEC filing. What Happened: A Form 4 filing from the U.S. Securities and Exchange Commission on Tuesday showed that WALTON sold 5,746,226 shares of Walmart. The total transaction amounted to $442,774,830. At Wednesday morning, Walmart shares are down by 1.36%, trading at $77.73. Get to Know Walmart BetterWalmart serves as the preeminent retailer in the United States, with its strategy predicated on superior operating efficiency and offering the lowest priced goods to consumers to…