procedure TMainForm.AddNode(Node: PNode; TreeNode: TTreeNode);
var
    NewNode: TTreeNode;
begin
    if Node <> nil then
    begin
        NewNode := TreeView.Items.AddChild(TreeNode, IntToStr(Node.Value));
        if (TreeNode <> nil) and (Node.Value < StrToInt(TreeNode.Text)) then
            NewNode.Enabled := False;

        if Node.Right <> nil then
            AddNode(Node.Right, NewNode);

        if Node.Left <> nil then
            AddNode(Node.Left, NewNode);
    end;
end;