Wal-Mart Stores reached an agreement with Live Nation Entertainment to sell tickets to concerts and other events at about 500 stores. The service will be introduced in the next few months in cities including Chicago and Los Angeles, according to Irving Azoff, executive chairman of Live Nation. The new accord will let Wal-Mart shoppers buy tickets for concerts, sports and other events at cash registers in the retailer's entertainment department, Mr. Azoff said. Live Nation also sells tickets at Blockbuster stores.