9 oz. pkg Fat-Free Cool Whip
1 c. nonfat plain yogurt
1/2 c. key lime juice
1 can fat-free condensed milk
1 lime for garnish (optional)
2 c. low-fat graham cracker crumbs
1/4 c. Sugar Twin
1/4 c. Fleischman's fat-free butter-like spread

CRUST
Mix crumbs, sugar twin and butter-like spread. If not to "crust" consistency, you add enough water enough to get this consistency. Pat into bottom of 9x13 pan or casserole, reserving a little for topping.
PIE
Mix Cool Whip, yogurt, lime juice, and condensed milk. Pour over crust and sprinkle remaining crumbs over top. If desired, top with zest from a lime. Put in freezer, serve directly from freezer. It thaws in minutes.