VBA - Ajout valeur si celulle voisine saisie (sur une plage)

Option Explicit

Sub test()
Dim derniere_ligne As Long, i As Long
derniere_ligne = Feuil1.Cells(Rows.Count, 1).End(xlUp).Row ' feuille 1
For i = derniere_ligne To 1 Step -1 ' jusquà la 1ere ligne
If Cells(i, 1) <> "" Then Cells(i, 2) = "X"
Next i
End Sub

For i = 1 To 200
    If Cells(1, 1) <>"" Then Cells(1, 2 = "x")
Next i

Option Explicit

Sub test()
Dim derniere_ligne As Long, i As Long
Application.ScreenUpdating = False
derniere_ligne = Feuil1.Cells(Rows.Count, 1).End(xlUp).Row ' feuille 1
For i = derniere_ligne To 1 Step -1 ' jusquà la 1ere ligne
If Cells(i, 1) <> "" Then Cells(i, 2) = "X"
Next i
Application.ScreenUpdating = True
End Sub

Private Sub Worksheet_Change(ByVal T As Range)
If Not Intersect(T, [A1:A200]) Is Nothing Then
If Len(T) > 0 Then T.Offset(, 1).Value = "X"
End If
End Sub