OK seems like i still don´t understand, how you change the range with only have a pubkey.
I read and read but don´t understand it, if i have a a pubkey and wanna reduce the range, it will come to a point where the dez value is odd and the whole thing go in a "never ending" story.

But i know there is a way, because you all talk about it in different posts. Maybe somebody explain it, in one easy to understand way.