CompUSA Inc warns that sales for the quarter ending June 25 will likely be lower than expected: its margins are not expected to improve from levels of the preceding two fiscal quarters; if sales and margin trends for the first two periods of the quarter continue, CompUSA will not be profitable during the fourth quarter, although it is too early to make any specific forecast; it says it hopes to open at least 10 new stores and relocate three stores in fiscal 1995.