Combine sugar, corn meal, and flour. Melt the margarine and add to the sugar mixture. Cream well. Add eggs, one at a time and beat thoroughly after each. Add vinegar, vanilla, and milk. Beat thoroughly. Pour into unbaked pastry shell and bake in a 400 deg. oven for 10 minutes, reduce heat to 325 deg. and continue baking 30 to 45 minutes or until set.