'nécessite une TextBox et  une PictureBox
'capture visible ici  :  http://img99.imageshack.us/img99/9449/sanstitre2yn6.jpg
'
Option Explicit
Private Declare Function CreateCaret Lib "user32" (ByVal hwnd As Long, ByVal hBitmap As Long, ByVal nWidth As Long, ByVal nHeight As Long) As  Long
Private Declare Function ShowCaret Lib "user32" (ByVal hwnd As Long) As Long
'
'
'**********************
'
'
Private Sub Form_Load()
'   créé  l'image
    With Picture1
        .Width = 135
        .Height = 255
        .Picture = .Image
        .Visible = False
    End With
End Sub
Sub Text1_GotFocus()
    Dim h As Long, p As Long
    h& = Text1.hwnd
    p& = Picture1.Picture
    CreateCaret h&, p&, 0, 0
    ShowCaret h&
End Sub
'
'
'**********************
'
' VOUS POUVEZ PASSER PAR UN OBJET  STDPICTURE POUR éVITER LA PICTUREBOX :
'
'
Dim O As New StdPicture
Private Sub Form_Load()
    Set O = LoadPicture("C:\c.jpg")
End Sub
Sub Text1_GotFocus()
    CreateCaret Text1.hwnd, O.Handle, 0, 0
    ShowCaret Text1.hwnd
End Sub

'   nécessite une textbox 
'   capture visible ici :  http://img138.imageshack.us/img138/6844/tten8.jpg 
Public Class Form1 
Private Declare Sub CreateCaret Lib "user32" (ByVal hwnd As Integer, ByVal hBitmap As Integer, ByVal nWidth As Integer, ByVal nHeight As Integer) 
Private Declare Function ShowCaret Lib "user32" (ByVal hwnd As Integer) As Integer 
Dim Img As New Bitmap("D:\c.jpg") 
Private Sub TextBox1_GotFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.GotFocus 
Dim h As Integer = TextBox1.Handle 
Dim p As Integer = Img.GetHbitmap.ToInt32 
        CreateCaret(h, p, 0, 0) 
        ShowCaret(h) 
End Sub 
Private Sub Form1_Disposed(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Disposed 
        Img.Dispose() 
End Sub 
End Class                                             

//Nécessite une Textbox nommé pour l'exemple TextBox1
public class Form1
{
    [DllImport("user32.dll",SetLastError=True)]
    static extern bool CreateCaret(IntPtr hWnd, IntPtr hBitmap, int nWidth, int nHeight);
    [DllImport("user32.dll",SetLastError=True)]
    static extern bool ShowCaret(IntPtr hWnd);
    Bitmap _caretBitmap = new Bitmap(@"C:\VotreCaret.jpg");
    Private void TextBox1_GotFocus(object sender,eventArgs e)
    {
       IntPtr hTextBox1 = TextBox1.Handle;
       IntPtr hCaretBitmap = _caretBitmap.GetHBitmap();
       CreateCaret(hTextBox1, hCaretBitmap,0,0);
       ShowCaret(hTextBox1);
    }