Tri-state for TreeNodes checkbox

There's something that would seem to me to be as common as mud in terms of*a typical*requirement in a*TreeView, but I can't see an simple answer.

That is to have an "Indeterminate" (appearing shaded) state of a node's checkbox, like a CheckBox control's CheckState property equalling CheckState.Indeterminate.

The obvious use for this is indicating whether some (but not all) child nodes are checked.* But since a TreeNode's Checked property is simply Boolean, I can't see a simple way of achieving this.*

Am I missing something really obvious here?* By the way, talking Windows forms, not web controls.