Mix flour, oatmeal, brown sugar, and margarine. Spread out and press onto a cookie sheet. Bake at 350 degrees for 15 minutes, stirring once. Should be crumbly. Cool and crumble up. Butter a 9×13 pan. Spread 1/2 of the crumb mixture on bottom. Cut ice cream into slices about 1/2 inch thick and lay in a single layer on crumbs. Drizzle with 1/2 of the caramel topping. Next layer 1/4 of crumbs, another layer of ice cream, then 1/4 of crumbs again. Top with remaining caramel topping and freeze until firm.