Bad news, you can't. There are so many hacks for them and none of them are good solutions. Javascript as described is the only way to do it but it takes too much bandwidth over little things but useful IF you plan to use jQuery for other functions.
CSS 3 has new rules that let you have that flexibility but many browsers don't offer full CSS 3 support. Since you wanted IE6/7, you're out of luck.
If it's REALLY that important, it's OK to use minimal tables. Don't let others tell you that it's wrong when it works for virtually all desktop browsers and even mobile browsers work just fine as long as they are not nested no more than two levels deep.
Another solution is to create layout designs that don't depend on checking other DIV's heights.