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'Controls - How to lowercase the text entered in text box using API
Option Explicit
 
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hWnd As Long, _
    ByVal nIndex As Long) As Long
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, _
    ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Const GWL_STYLE = (-16)
Private Const ES_LOWERCASE As Long = &H10&
 
Private Sub Form_Load()
    Dim style As Long
 
    ' Get the current style.
    style = GetWindowLong(Text1.hWnd, GWL_STYLE)
 
    ' Add ES_LOWERCASE to the style.
    SetWindowLong Text1.hWnd, GWL_STYLE, style Or ES_LOWERCASE
End Sub