How can I get a tooltip to vary from node to node in my treeview

Try using a MouseMove event handler and
checking to see if you have moved to a new node, and if so, set a new
tiptext.

[C#]
 	private int oldNodeIndex = -1;
	private ToolTip toolTip1;

	private void Form1_Load(object sender, System.EventArgs e)
	{
		this.toolTip1 = new System.Windows.Forms.ToolTip();
		this.toolTip1.InitialDelay = 300; //half a second delay
		this.toolTip1.ReshowDelay = 0;
	}
	
	private void treeView1_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
	{
		TreeNode tn = this.treeView1.GetNodeAt(e.X, e.Y);
		if(tn != null)
		{
			int currentNodeIndex = tn.Index;
			if(currentNodeIndex != oldNodeIndex)
			{
				oldNodeIndex = currentNodeIndex;
				if(this.toolTip1 != null && this.toolTip1.Active)
					this.toolTip1.Active = false; //turn it off

				this.toolTip1.SetToolTip(this.treeView1, string.Format('tooltip: node {0}', oldNodeIndex));
				this.toolTip1.Active = true; //make it active so it can show
			}
		}
	}

[VB.NET]
	Private oldNodeIndex As Integer = - 1
	Private toolTip1 As ToolTip


	Private Sub Form1_Load(sender As Object, e As System.EventArgs)
   		Me.toolTip1 = New System.Windows.Forms.ToolTip()
   		Me.toolTip1.InitialDelay = 300 ’half a second delay
   		Me.toolTip1.ReshowDelay = 0
	End Sub ’Form1_Load


	Private Sub treeView1_MouseMove(sender As Object, e As System.Windows.Forms.MouseEventArgs)
   		Dim tn As TreeNode = Me.treeView1.GetNodeAt(e.X, e.Y)
   		If Not (tn Is Nothing) Then
      			Dim currentNodeIndex As Integer = tn.Index
      			If currentNodeIndex <> oldNodeIndex Then
         			oldNodeIndex = currentNodeIndex
         			If Not (Me.toolTip1 Is Nothing) And Me.toolTip1.Active Then
            				Me.toolTip1.Active = False ’turn it off
         			End If
         			Me.toolTip1.SetToolTip(Me.treeView1, String.Format('tooltip: node {0}', oldNodeIndex))
         			Me.toolTip1.Active = True ’make it active so it can show
      			End If
   		End If
	End Sub ’treeView1_MouseMove