I figured out one way to get this to work, although I'm not sure how susceptible it is to change:
String TClientID = TreeViewControl.ClientID;
int n = 0;
If you increment N for each node you process, starting at the root node, then the following will work:
Node.NavigateUrl =
"javascript:TreeView_ToggleNode(" + TClientID + "_Data," + n.ToString() + "," + TClientID + "n" + n.ToString() + ",' '," + TClientID + "n" + n.ToString() + "Nodes)";
I'm open to comments / suggestions on this code.
-Craig