DataGridView

I am missing something in my sample code that allows me to save changes in the datagrid back to the structure.  Could I get a good pointer as to what that might be?

Public Class Form1
    Private Tests As New Generic.List(Of testdata)
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Tests.Add(New testdata("John", "Smith", 48))
        Tests.Add(New testdata("Jane", "Smith", 45))
        Tests.Add(New testdata("Andy", "Smith", 19))
        Tests.Add(New testdata("Sally", "Smith", 23))
        With Me.DataGridView1
            Dim binder As New BindingSource
            binder.DataSource = Tests
            .DataSource = binder
            .ReadOnly = False
            .EditMode = DataGridViewEditMode.EditOnKeystroke
            .Columns("Forename").HeaderText = "First Name"
            .Columns("Forename").ReadOnly = True
            .Columns("Surname").HeaderText = "Family Name"
            .Columns("Surname").ReadOnly = True


        End With


    End Sub

    Private Sub DataGridView1_CellEndEdit(sender As Object, e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellEndEdit

    End Sub

    Private Sub DataGridView1_CellLeave(sender As Object, e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellLeave

    End Sub
End Class

Public Structure testdata
    Public Sub New(FName As String, SName As String, Years As Integer)
        Forename = FName
        Surname = SName
        Age = Years
    End Sub

    Private _Forename As String
    Public Property Forename As String
        Get
            Return _Forename
        End Get
        Set(value As String)
            _Forename = value
        End Set
    End Property

    Private _Surname As String
    Public Property Surname As String
        Get
            Return _Surname
        End Get
        Set(value As String)
            _Surname = value
        End Set
    End Property

    Private _Age As Integer
    Public Property Age As Integer
        Get
            Return _Age
        End Get
        Set(value As Integer)
            _Age = value
        End Set
    End Property

    Public Property RecordColour As Color

End Structure