override a treenode class in c#

Hi all,

      I want a customized treeview where i want checkbox in a haphazard manner for eg. sometime i want to add checkbox in both parent and child node, and sometimes only in child node. for that i am trying to override the TreeNode class,so that i can add that class object(node) when i need a node with checkbox else the default TreeNode object(for this node.DrawDefault = false) but not getting any clue. Can somebody plz help me out.

Thanks in advance