Help with SICP

http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-10.html#%_sec_1.1.6
Exercise 1.3 is a bitch. I think I'm close to a solution, then I see a fundamental flaw, and have to rewrite it. My notebook paper hurts.

You guys should think simpler. If the procedure operates on the two higher values and there's three values, then it's easier to just check for the low value and operate on the other two.