Private Declare Function CreateCaret Lib "user32" _
 (ByVal hWnd As IntPtr, ByVal hBitmap As IntPtr, _
  ByVal nWidth As Integer, _
  ByVal nHeight As Integer) As <MARSHALAS(UNMANAGEDTYPE.BOOL)>Boolean
Private Declare Function ShowCaret Lib "user32" _
 (ByVal hWnd As IntPtr) As <MARSHALAS(UNMANAGEDTYPE.BOOL)>Boolean
 CreateCaret(TextBox1.Handle, IntPtr.Zero, 15, 15)
 ShowCaret(TextBox1.Handle)