I have trouble in manipulating the fonts of double style list box. Please help.

It is easy to maniputlating the font of single style list box. It can be done by:

ListBox->ItemDrawer()->ColumnData()->SetColumnFontL( 1, LatinBold17() );

I tried the similar way to manipulate the fonts of double style list box:

ListBox->ItemDrawer()->FormattedCellData()->SetSubCellFontL( 1, LatinBold17() );
ListBox->ItemDrawer()->FormattedCellData()->SetSubCellFontL( 2, LatinBold13() );

But the above two lines just do nothing. Why?