Public Class Form1
    Inherits System.Windows.Forms.Form
    '// Designer
 
   Private Sub H_Scroll(ByVal sender As Object, ByVal e As EventArgs)
        Debug.WriteLine("h_scroll")
    End Sub
 
    Private Sub V_Scroll(ByVal sender As Object, ByVal e As EventArgs)
        Debug.WriteLine("v_scroll")
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        Dim lv As New MyListBox
        lv.HorizontalScrollbar = True
        AddHandler lv.H_Scroll, AddressOf H_Scroll
        AddHandler lv.V_Scroll, AddressOf V_Scroll
        For a As Integer = 0 To 1000
            lv.Items.Add(New String(CChar(a.ToString), 30))
        Next
        Me.Controls.Add(lv)
    End Sub
 
End Class
 
Public Class MyListBox
    Inherits ListBox
 
    Public Event V_Scroll(ByVal sender As Object, ByVal e As EventArgs)
    Public Event H_Scroll(ByVal sender As Object, ByVal e As EventArgs)
    Private Const WM_VSCROLL As Int32 = &H115
    Private Const WM_HSCROLL As Int32 = &H114
 
    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        If m.Msg = Me.WM_HSCROLL Then
            RaiseEvent H_Scroll(Me, New EventArgs)
        ElseIf m.Msg = Me.WM_VSCROLL Then
            RaiseEvent V_Scroll(Me, New EventArgs)
        End If
        MyBase.WndProc(m)
    End Sub
 
End Class