PREHEAT oven to 350°F. Microwave 5 Tbsp. of the margarine in medium microwaveable bowl on HIGH 30 sec. or until melted. Add wafer crumbs and pecans; mix well. Press firmly onto bottom and up side of 9-inch pie plate. Bake 10 min. Cool completely; set aside.
PLACE caramels, 2 Tbsp. of the cream and the remaining 1 Tbsp. margarine in small saucepan; cook on low heat until caramels are completely melted and mixture is well blended, stirring frequently. Pour into prepared crust; cool while preparing filling.
SPRINKLE gelatine over cold water in small saucepan; let stand 1 min. Cook on low heat 5 min. or until gelatine is completely dissolved, stirring frequently. Stir in 1/2 cup of the cream and the chocolate. Cook until chocolate is completely melted, stirring frequently. Cool 15 min. Beat 1 cup of the cream and the vanilla in large bowl with electric mixer on medium speed until thickened. Gradually add chocolate mixture, beating until light and fluffy. Spread over caramel layer in crust. Refrigerate 3 hours or until firm. Beat remaining cream with electric mixer until stiff peaks form. Spoon over pie just before serving. Store leftover pie in refrigerator.