SICP Exercise 1.3

Exercise 1.3.  Define a procedure that takes three numbers as arguments and returns the sum of the squares of the two larger numbers.

(define (ex3 x y z)
                     (cond
                       ((> y z x) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> y x z) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> z y x) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> z x y) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> x z y) ((define a x) (define b y) (+ (square a) (square b))))
                       ((> x y z) ((define a x) (define b y) (+ (square a) (square b)))))

I know I'm thinking about this the wrong way. My solution doesn't work.

>>8
The question is;

Give a method with the lowest number of comparisons for finding the two greatest numbers out of a set of three numbers.

to all the code monkeys on /prog/, this is the pure computer science shit you will never, ever know.