Preheat oven to 350 degrees. Grease and flour a 15x19x1 inch baking pan or a 13x9 inch pan.
In a large bowl, combine cake mix, cherry pie filling, vanilla, and eggs. Mix until combined and moistened. Spread in the prepared pan.
If using a 15x10x1 inch pan bake for 20-30 minutes. If using a 9x13 inch bake for 25-30 minutes or until toothpick inserted in center comes out clean. Remove from oven and let cool.
To make the frosting, In a small saucepan, combine sugar, milk, and margarine. Bring to a boil. Boil for about 1 minute and remove from heat. Stir in chocolate chips until melted and smooth. Pour over the sheet cake and spread evenly over