Preheat oven to 375°. In small bowl, mix crumbs, flour and baking powder. In large mixing bowl, beat margarine; add condensed milk and beat until blended and smooth. Add cracker mixture. Stir in coconut, chips and walnuts. Spray cooking spray on cookie sheets. Drop by rounded tablespoons onto sheets and slightly flatten with spoon (wet spoon, if necessary). Bake 10 to 12 minutes, or until lightly browned. Let set on cookie sheet 1 to 2 minutes after baking, then loosen carefully with spatula. Store loosely covered at room temperature or freeze for longer freshness.