Preheat oven to 350. Prepare a 9"x13" pan with cooking spray; set aside. To prepare crust, combine flour, pecans, brown sugar, and margarine. Mix until crumbly. Reserve half cup crumbs for topping. Press remaining mixture onto bottom of prepared pan. Bake for 15 minutes, or until lightly browned. Meanwhile, for filling, combine, Just Whites, sugar, water, and lemon juice. Mix for ten minutes, or until stiff. Fold in strawberries and whipped topping. Spread mixture evenly over baked crust. Sprinkle reserved crumb mixture over top. Freeze dessert for several hours before serving.