Public Class Form1
    Private rect, prect As Rectangle, vrect As Boolean
    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        If vrect Then
            ControlPaint.DrawReversibleFrame(rect, Color.Black, _
              FrameStyle.Dashed)
            Windows.Forms.Cursor.Clip() = Screen.PrimaryScreen.WorkingArea
            If e.Button = Windows.Forms.MouseButtons.Right AndAlso rect.Width _
              > 0 AndAlso rect.Height > 0 Then
                Using bmp As New Bitmap(rect.Width, rect.Height), g As Graphics _
                = Graphics.FromImage(bmp)
                    g.DrawImage(PictureBox1.Image, 0, 0, prect, _
                    GraphicsUnit.Pixel)
                    PictureBox2.Image = bmp
                    PictureBox2.Refresh()
                End Using
            End If
            rect = Nothing
            vrect = False
        Else
            rect.Location = PictureBox1.PointToScreen(e.Location)
            prect.Location = e.Location
            vrect = True
            Windows.Forms.Cursor.Clip() = RectangleToScreen(PictureBox1.Bounds)
        End If
    End Sub
    Private Sub PictureBox1_MouseMove(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        If vrect AndAlso e.Button = Windows.Forms.MouseButtons.Left Then
            ControlPaint.DrawReversibleFrame(rect, Color.Black, _
              FrameStyle.Dashed)
            rect.Size = New Size(Windows.Forms.Cursor.Position.X - rect.X, _
            Windows.Forms.Cursor.Position.Y - rect.Y)
            prect.Size = rect.Size
            ControlPaint.DrawReversibleFrame(rect, Color.Black, _
              FrameStyle.Dashed)
        End If
    End Sub
End Class