incrémenation valeur VBA

Private Sub worksheet_change(ByVal target As Range)
If Not Intersect(target, Range("B6:B" & Range("B65535").End(xlUp).Row + 1)) Is Nothing Then
If target = target.Offset(-1, 0) Then
Cells(target.Row, 1) = Cells(target.Row - 1, 1) + 50
Else
Cells(target.Row, 1) = 50
End If
End If
End Sub

Private Sub Workbook_Activate()
' ici on récupère les données en colonne B
'
'
' et ensuite  on met les valeurs en colonne A
For Each cellule In Range("B6:B" & Range("B65535").End(xlUp).Row)
If cellule.Offset(-1, 0) = cellule Then
Cells(cellule.Row, 1) = Cells(cellule.Row - 1, 1) + 50
Else
Cells(cellule.Row, 1) = 50
End If
Next cellule
End Sub

=SI(B5<>B6;50;A5+50)

Private Sub Worksheet_Change(ByVal Target As Range)
If Intersect(Target, [B:B]) Is Nothing Then Exit Sub
With Range("A6:A" & [B65536].End(xlUp).Row)
  .FormulaR1C1 = "=IF(R[-1]C2<>RC2,50,R[-1]C+50)"
  .Value = .Value 'supprime les formules
  Range("A" & .Count + 6 & ":A" & Rows.Count).ClearContents
End With
End Sub