I do something similar, its a new kind of node you need to create, add a new class and it should look something like this... You would then just create a new one of your nodes
(myTreeNode aNode = new myTreeNode("SomeText", "Some other Text for Tag2"

)
and add it to the treeview in question. Namespace etc will be whatever you need, this is just cut and pasted from one of my recent projects to give you an idea.
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
namespace ttControls
{
/// <summary>
/// Summary description for Class1.
/// </summary>
public class myTreeNode : TreeNode
{
private string Tag2;
public myTreeNode(string myText, int myTag)
{
//
// TODO: Add constructor logic here
//
this.Text=myText;
this.Tag2=myTag;
}
public string tag2
{
get {return Tag2;}
}
}
}