Option Explicit
Sub Ligne_insérer()
Dim i As Long
Application.ScreenUpdating = False
Columns(1).SpecialCells(xlCellTypeBlanks).Delete Shift:=xlUp
For i = Cells(Rows.Count, "a").End(xlUp).Row To 2 Step -1
If Range("a" & i) <> Range("a" & i).Offset(-1, 0) Then Rows(i).Insert
Next i
Application.ScreenUpdating = True
End Sub