Blind-bake piecrust; cool.
In medium saucepan, stir together 2/3 cup sugar, cornstarch, salt and 3 cups milk; blend in eggs. Cook over medium heat, stirring constantly, until mixture boils; boil and stir 1 minute.
Remove from heat; stir in butter and vanilla. Into small bowl, pour 1-1/2 cups cream filling; stir in coconut. Set aside.
Stir together cocoa, 3 tablespoons sugar and 2 tablespoons milk; blend into remaining cream filling in saucepan.
Return to heat; cook just to boiling, stirring constantly. Remove from heat; pour
1 cup chocolate filling into baked pie crust. Spread coconut filling over chocolate layer. Top with remaining chocolate filling; spread evenly.
Press plastic wrap directly onto surface; refrigerate 6 to 8 hours.
Just before serving, spread with whipped topping. Cover; refrigerate leftover pie. 8 servings.