ListView1.FlatScrollBar = True

' Klappt bei Mir ohne Probleme. 
' (Natürlich Vorausgesetzt, der View steht auf Report und der
' ColumnHeader existiert)
ListView1.View = lvwReport
ListView1.ColumnHeaders(1).Width = 2000

Const HDS_BUTTONS As Long = &H2
Const GWL_STYLE As Long = (-16)
Const LVM_FIRST As Long = &H1000
Const LVM_GETHEADER As Long = (LVM_FIRST + 31)
 
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
    (ByVal hwnd As Long, _
     ByVal wMsg As Long, _
     ByVal wParam As Long, _
     lParam As Any) As Long
 
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 Sub FlatColumnHeader(oLSV As MSComctlLib.ListView)
  '--------------------------------------------------
  Dim lStyle       As Long
  Dim lHeader      As Long
  On Error GoTo Error_
  '--------------------------------------------------
  ' Handle des ColumnHeader holen
  lHeader = SendMessage(oLSV.hwnd, LVM_GETHEADER, 0, ByVal 0&)
  ' Aktuelles Aussehen des Headers lesen
  lStyle = GetWindowLong(lHeader, GWL_STYLE)
   '--------------------------------------------------
  ' Aktuelles "Style" ändern
  lStyle = lStyle Xor HDS_BUTTONS
  If lStyle Then
    ' neues Style setzen
    Call SetWindowLong(lHeader, GWL_STYLE, lStyle)
  End If
  '--------------------------------------------------
  Exit Sub
Error_:
End Sub