How do I call Script Notify on Touch action (Windows Phone )

Hi all, I want a button that when touched, It's prompt a window to share my game on social network (FB, tweeter,...).

I can find the way to use Facebook object, so I have a work around by using ShareLinkTask of Windows phone. In order to do that, I think I need to notify native code by javascript. I've tried to do this:

But it seem to be does not work at all. Can anyone give me some advices? Thank you very much