H Sam,

Because the children have a different class (or at least you can make it that way) you can effectively hide them from view.
Long long ago I was involved with a hack that made a collapsible tree menu. If memory serves me well, I made a 2.x version. Go hunt the forums.

Good luck

You're right, I forgot about hiding. So this code does what I need, this is good enough. I don't wanna hack the core.

div.bSideItem ul ul { display:none }

Thanks