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.

#define MIN( a , b ) ((a<b)?a:b)
#define MAX( a , b ) ((a>b)?a:b)

#define SQUARE( x ) (x*x)

uint32_t ex3(uint32_t x, uint32_t y, uint32_t z)
{
        return (SQUARE(MAX(x,y)) + (SQUARE(MAX(MIN(x,y),z))));
}