Change Property of BoxView inside ListView

Hi.
I have ListView Where first column contains base information and second column contains only 1px green BoxView where by default it is IsVisible property is set to false. And now i want OnItemSelected event of ListView show specific BoxView.

But i can not get element inside ListView.

i try somethink :

    var bxView = this.Content.FindByName<BoxView>("box178");    
      if (bxView != null)    
         bxView.IsVisible = true;

Have anyone solved this problem?