Public Class Form1
    Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
      ByVal hwnd As IntPtr, ByVal wMsg As Integer, _
    ByVal wParam As Integer, ByVal lParam As String) As Integer
    Const WM_VSCROLL As Int32 = &H115
    Const SB_UP As Int32 = 0             ' 1 Zeile hoch
    Const SB_DOWN As Int32 = 1           ' 1 Zeile runter
    Const SB_PAGEUP As Int32 = 2         ' 1 Seite hoch
    Const SB_PAGEDOWN As Int32 = 3       ' 1 Seite runter
    Const SB_TOP As Int32 = 6            ' ganz nach oben
    Const SB_BOTTOM As Int32 = 7         ' ganz nach unten
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        SendMessage(RichTextBox1.Handle, WM_VSCROLL, SB_PAGEDOWN, Nothing)
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        RichTextBox1.ScrollBars = RichTextBoxScrollBars.None   ' Scrollbalken 
        ' abschalten
    End Sub
End Class