CUT EACH TOMATO INTO 6 WEDGES. CUT PEPPER INTO 3 cm SQUARES. CUT CELERY INTO 1 cm SLANTED SLICES. CUT BEEF INTO 4 cm WIDE STRIPS WITH THE GRAIN, THEN CUT INTO 0 cm SLICES ACROSS THE GRAIN. IN A BOWL, STIR TOGETHER CORNSTARCH, SOY, SHERRY, AND WATER. ADD MEAT AND STIR TO COAT, THEN STIR IN 1.5 TEASPOONS OF OIL AND MARINATE FOR AT LEAST 15 MINUTES. MEANWHILE PREPARE COOKING SAUCE AND SET ASIDE. PLACE STIR-FRY PAN OVER HIGH HEAT, WHEN HOT ADD 2 TABLESPOONS OF OIL. WHEN OIL BEGINS TO HEAT, ADD GINGER AND GARLIC AND STIR ONCE. ADD MEAT MIXTURE AND STIR FRY UNTIL MEAT IS BROWNED ( 1.5 TO 2 MINUTES). REMOVE FROM PAN AND SET ASIDE. POUR REMAINING OIL INTO PAN. WHEN HOT, ADD CELERY AND ONION AND STIR FRY FOR 1 MINUTE. ADD BELL PEPPER AND STIR FRY FOR ONE MORE MINUTE. ADD A FEW DROPS OF WATER IF PAN LOOKS DRY. ADD TOMATOES AND STIR FRY FOR 1 MINUTE. RETURN MEAT TO PAN AND ADD COOKING SAUCE. STIR UNTIL SAUCE THICKENS. SEASON TO TASTE WITH SALT. MAKES 4 SERVINGS