>>You also get 3 states for values if 0 (false), 1 (true), and the indeterminate state for other than 0,1 values.
>
>In VFP, right?
>Do you know if the treeview in VFP supports checkboxes and if so does the checkboxes in the treeview support the 3rd state?

I think there's two versions of the treeview ActiveX floating around in use by VFP. One supports the checkbox (don't know about the 3 states), and the other doesn't have any checkbox.

[update]
I just looked into (V5/sp2) no checkbox. V6 (with checkbox) only support 0/non-zero and .t./.f., no .null. value. Both Microsoft controls.