Public Class MyTB : Inherits TextBox
   <DllImport("user32.dll", SetLastError:=True)> _
   Private Shared Function CreateCaret(ByVal hWnd As IntPtr, ByVal hBitmap As IntPtr, ByVal nWidth As Integer, ByVal nHeight As Integer) As Boolean
   End Function

   <DllImport("user32.dll")>
   Private Shared Function DestroyCaret() As Boolean
   End Function

   <DllImport("user32.dll")>
   Private Shared Function SetCaretBlinkTime(ByVal uMSeconds As UInt32) As Boolean
   End Function

   <DllImport("user32.dll")> _
   Private Shared Function ShowCaret(ByVal hWnd As IntPtr) As Boolean
   End Function

   Protected Overrides Sub OnGotFocus(e As EventArgs)
      MyBase.OnGotFocus(e)
      MyTB.CreateCaret(Me.Handle, Nothing, 5, Me.Font.Height)
      MyTB.SetCaretBlinkTime(500UI)
      MyTB.ShowCaret(Me.Handle)
   End Sub

   Protected Overrides Sub OnLostFocus(e As EventArgs)
      MyBase.OnLostFocus(e)
      MyTB.DestroyCaret()
   End Sub
End Class