Private Sub Form_Load()
    SendMessage Text1.hwnd, _
        EM_LIMITTEXT, 4, 0
    SendMessage Combo1.hwnd, _
        CB_LIMITTEXT, 4, 0

    SendMessage Text2.hwnd, _
        EM_LIMITTEXT, 8, 0
    SendMessage Combo2.hwnd, _
        CB_LIMITTEXT, 8, 0
End Sub