Sub inserer_colonnes()
Application.ScreenUpdating = False
lastcol = Cells(2, Columns.Count).End(xlToLeft).Column
For n = 9 To lastcol
If Month(Cells(2, n + 1)) <> Month(Cells(2, n)) Then
Cells(2, n + 1).EntireColumn.Insert Shift:=xlRight
n = n + 1
End If
Next
Application.ScreenUpdating = True
End Sub