Heat oven to 375*F. Mix together graham cracker crumbs, flour and baking powder. With mixer, beat sweetened condensed milk and margarine until smooth. Add crumb mixture; mix well. Stir in raisins, coconut and walnuts. Drop tablespoons onto lightly greased cookie sheets Bake 9 to 10 minutes or until lightly browned. Cool 2 to 3 minutes; remove from cookie sheets. Store loosely covered at room temperature. Makes about 3 dozen.