CUT EACH TOMATO INTO 6 WEDGES. CUT PEPPER INTO 1" SQUARES. CUT CELERY INTO 1/4" SLANTED SLICES. CUT BEEF INTO 1 1/2" WIDE STRIPS WITH THE GRAIN, THEN CUT INTO 1/8" SLICES ACROSS THE GRAIN. IN A BOWL, STIR TOGETHER CORNSTARCH, SOY, SHERRY, AND WATER. ADD MEAT AND STIR TO COAT, THEN STIR IN 1 1/2 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 1/2 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