Private Sub txtTest_Change()
   
     Call adhLimitChars(txtTest, Val(txtValue))
End Sub

Option Compare Database
Option Explicit

' From Access 2002 Desktop Developer's Handbook
' by Litwin, Getz, and Gunderloy. (Sybex)
' Copyright  2001 .  All rights reserved.

Private Declare Function SendMessageLong _
 Lib  "user32"  Alias  "SendMessageA"  _
 (ByVal hWnd As Long, ByVal wMsg As Long, _
 ByVal wParam As Long, lngValue As Long) As Long

Private Declare Function GetFocus _
 Lib  "user32"  () As Long

Private Const EM_SETLIMITTEXT As Long = &HC5

Public Sub adhLimitChars(txt As TextBox, lngLimit As Long)
 
    Dim hWnd As Long
    Dim lngResult As Long
    Dim lngNewMax As Long
    
    ' Get the window handle for the current window.
    hWnd = GetFocus()
    
    ' Hey, what if there's ALREADY too much text in
    ' there?  Limiting the text would make it
    ' impossible to type in there at all.  You want
    ' to set the limit to be the max of the amount
    ' you want and the amount that's in there!
    lngNewMax = Len(txt.Text)
    If lngNewMax < lngLimit Then
        lngNewMax = lngLimit
    End If
    
    ' Send the message to the current text box
    ' to limit itself to lngNewMax characters.
    SendMessageLong hWnd, EM_SETLIMITTEXT, lngNewMax,  0 
End Sub