Possible to enable vertical lines for tree component in my theme?

["Adam B" <cruxic gmail com>]

Hi folks,

I am working on a theme and I would like the hierarchical tree views to show dotted vertical lines so the indent level is very clear.  Is this possible?  The following did not work for me:

style "mystyle"
{
GtkTreeView::enable-grid-lines = GTK_TREE_VIEW_GRID_LINES_VERTICAL
...

  engine "redmond95" 
    {

    }
}

Any hints would be appreciated.
Thanks.
- Cruxic