Japanese phrase help

How do you say that (something) is possible/impossible if you (do this/not do this) in Japanese?

that (something) is possible.
それは可能です。
that (something) is impossible.
それは不可能です。

It is possible if you do it.
やればできる(yareba dekiru)
- common phrase

It is possible if you do it.
なせばなる(naseba naru)
It is impossible if you not do it.
なさねばならぬ(nasaneba naranu)
- classical phrase, old-fashioned/formal sounds

from Uesugi Yozan's famous saying,
なせばなる、なさねばならぬ、なにごとも
ならぬは、ひとのなさぬ なりけり
(naseba naru, nasaneba naranu, nanigoto mo
naranu wa hito no nasanu nari keri)
Do and it will be done, don't do and it will not be done
if something is not done, that is because no one did it.
http://en.wikipedia.org/wiki/Uesugi_Harunori

Please post a full sentence (in English) of what you want to say... :)

Thanks for the help.

Is it something different from "...ことができまる"