Beat whipping cream until foamy; gradually add sugar, beating until soft peaks form.
Fold in macaroon crumbs, pecans, and vanilla.
Spread half of macaroon mixture in bottom of a two-piece 10-inch tube pan.
Spread raspberry sherbet evenly over macaroon mixture; freeze 30 minutes.
Repeat with other sherbets, freezing 30 minutes between layers.
Top with remaining macaroon mixture, and freeze until firm.
Let frozen dessert stand at room temperature 10 minutes before serving.
Remove side piece of tube pan; slice.