[Shizuka]

Dear all,
I've a problem that's bugging me almost since the day I bought my Kindle 3. I read both books bought by amazon and books bought or written in other format ( i.e html, doc, odt and pdf). I find very usefull the feature of searching in the english default dictionary during the reading ( I'm not a native english spieaker) but I don't know how to make available this feature also for books that aren't native mobi.
For examble:
I've the novel "novel.odt" and I want to convert it in mobi to be able to read on my kindle. How do I have to do so the I'd able to use the search feature on this (new) mobi? What parameter, feature or setting I have to focus on?

Thanks in advance
Shizuka