user-defined type not define

[LV err]

Private Const LVM_FIRST As Long = &H1000
Private Const LVM_SETCOLUMNWIDTH As Long = (LVM_FIRST + 50)
Private Const LVSCW_AUTOSIZE_USEHEADER As Long = -2

Public Sub lvsizecolumns(lv As ListView) show error this line when I compile (user-defined type not define)
Dim Counter As Long
'Resizes Listview Column Headers.
For Counter = 0 To (lv.ColumnHeaders.Count - 1)
Call SendMessage(lv.hWnd, LVM_SETCOLUMNWIDTH, Counter, _
ByVal LVSCW_AUTOSIZE_USEHEADER)
Next Counter
End Sub

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