Can i navigate page from other page to appear in frame of Mainwindow ?

Question

i have two frames in Mainwindow forum. one page i able to navigate by direct clicking on button. but second page i could not because second page i am calling from first page to appear in second Frame of Mainwindow. i need it plz help ?

  private void open_btn_Click( object sender, RoutedEventArgs e )
  {
  Forms.user user = new Forms.user();
  hostfram.Navigate(user);
  hostfram.Refresh();
  }

this func. working good because calling from direct Mainwindow. but this

public  void Usernavigation( int number )
  {
  switch ( number )
  {
  case 0:
  Forms.cadastra cadastra = new Forms.cadastra();
  hostfram.Navigate(cadastra);
  break;
  }
  }
this not navigating page without any error because this i calling from first page to appear second page in Mainwindow how to do this ? i have lot of pages i must to do this