Hi,
just like you i searched for a dictionary a few weeks ago, that would satisfy my needs, but i didn't find any free one.
So i started to write my own. It's available here:
http://sourceforge.net/projects/engjapdictiona/.
It doesn't have the feature you mentioned just yet. But there's a forum available where you can post your ideas. If you could describe your exact idea, maybe a screenshot of an existing program that looks like you mean it, that would be great.
If you haven't already found a good one including your feature and are willing to wait a few days or a week maybe (can't tell just yet^^), i'm willing to implement any good idea.