Remove backbutton on a page that is not the current view?

Dilemma:

I navigate to page 1 from page 0 by by pushAsync(new Navigationpage(new Page1));
I land on page 1, that has a backbutton pointing to page 0. I now navigate to page2.
I land on page 2, that has i backbutton to page1. Here i do whatever.. and then press the backbutton to go to page1.

NOW I WANT THIS TO HAPPEN --> when i land on page1 there should no backbutton.

Allready tested:
-Setting NavigationPage.sethasBackbutton(this, false) by overriding "onappearing" on page1.
-Calling a function to page1 from page2, setting page1 backbutton to false.

Is there a way to disable backbutton and get it to change without "new"ing the page?

Thank you!