Line an 8 1/2- x 4 1/2- x 3-inch loafpan with plastic wrap, smoothing plastic wrap in corners and on sides of pan. Arrange one-third of ladyfinger halves, cut sides facing in, on bottom and around sides of loafpan; set aside.
Fold whipped topping into yogurt. Spoon half of yogurt mixture into prepared loafpan. Spoon 1/4 cup caramel syrup over yogurt mixture. Swirl caramel syrup with a knife to create a marbled effect. Arrange half of remaining ladyfinger halves on top of caramel. Repeat layers with remaining yogurt mixture, remaining 1/4 cup caramel syrup, and remaining ladyfinger halves. Cover and freeze at least 8 hours.
To serve, invert dessert onto a serving plate, carefully peeling away plastic wrap. Cut into 10 slices, and top evenly with raspberries.