The person making the horcrux has to WANT to make it, to be pure evil. Dumbledore may have not been the ultimately good wizard he was later in life, but he still tried to do the right thing. He wouldn't make one, even on accident. And in any case, the piece of the soul that is ripped out of your body when you make a horcrux has to be in a LIVING being, not a wand. So, it means that the Elder Wand was just the most powerful wand in the hands of the most powerful wizard. Even Voldy feared him. It's why he had someone else to his dirty work to kill Dumbledore. But it was a well thought out idea. Kudos for that!