LOBLAW COMPANIES LTD. $55 (www.loblaw.ca) is testing a smaller version of its discount No Frills supermarkets. These stores, which operate under the Box banner, are cheaper to build than full-sized outlets and can fit in smaller strip malls, which lowers their rental costs. The new Box stores could also help Loblaw compete with Wal-Mart, which may start opening smaller locations in Canada following successful trials in the U.S. Buy.