Function ScreenToPicture(ByVal Location As String, ByVal Format As _
  System.Drawing.Imaging.ImageFormat) As String
 
        Try
            Dim currentScreenSize As Size = New Size( _
              My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
            Dim ScreenToBitmap As New Bitmap(My.Computer.Screen.Bounds.Width, _
            My.Computer.Screen.Bounds.Height)
            Dim gGraphics As System.Drawing.Graphics = _
            System.Drawing.Graphics.FromImage(ScreenToBitmap)
 
            gGraphics.CopyFromScreen(New Point(0, 0), New Point(0, 0), _
              currentScreenSize)
 
 
            ScreenToBitmap.Save(Location, Format)
 
 
            Clipboard.SetImage(ScreenToBitmap)
 
            Return Location
 
        Catch ex As Exception
            Return ex.Message
        End Try
 
    End Function

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Button1.Click
        Timer1.Enabled = True
    End Sub

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Timer1.Tick
        Dim datei As String
        datei = "C:\Test01.jpg"
 
        If System.IO.File.Exists(datei) Then
            datei = "C:\Test02.jpg"
            ScreenToPicture(datei, System.Drawing.Imaging.ImageFormat.Jpeg)
        Else
            ScreenToPicture(datei, System.Drawing.Imaging.ImageFormat.Jpeg)
 
        End If
 
 
    End Sub