Possible Duplicate:
Tri-State Checkboxes in WinForms TreeView
How can I change the symbol within the parent node checkbox in treeview to a green box instead of a checkmark when only some of the children within the parent node are selected?
Example:

Possible Duplicate:
Tri-State Checkboxes in WinForms TreeView
How can I change the symbol within the parent node checkbox in treeview to a green box instead of a checkmark when only some of the children within the parent node are selected?
Example:

How about this code project that already did the work of creating a TriStateTreeView for you? Otherwise, you need to create your own control anyway