Markable list box

I'm using the following code to display a markable listbox.

//-------------------
iListBox = new (ELeave) CAknDoubleNumberStyleListBox;
iListBox->SetContainerWindowL( *this );
iListBox->ConstructL( this, EAknListBoxMarkableList);
iListBox->CreateScrollBarFrameL(ETrue);
iListBox->ScrollBarFrame()->SetScrollBarVisibilityL( CEikScrollBarFrame::EOff, CEikScrollBarFrame::EAuto);
iListBox->Model()->SetOwnershipType(ELbmOwnsItemArray);
iListBox->ActivateL();
//----------------

However, the 'ticks' aren't showing in the right hand margin.
What else must I do to display the ticks?


Cheers
Paris.