check/uncheck treeview in c# 4.0

When I check/uncheck a node in a TreeView, I want to see whether any of the parent nodes in the heirarchy are checkd.  I want to check/uncheck parent nodes accordingly.  I looked so many forums but no answer. 

If any of the parent node has a checked child node, I want to stop unchecking one level below this parent. Please help.

Cris Evan