Bonjour,
A tester.
Cdlt.
Public Sub DEMO()
Dim lastRow As Long, i As Long
Dim sOld As String, sNew As String
With ActiveSheet
lastRow = .Cells(Rows.Count, 1).End(xlUp).Row
For i = 2 To lastRow
sOld = .Cells(i, 6): sNew = .Cells(i, 7)
.Cells(i, 3).Value = Replace(.Cells(i, 3).Value, sOld, sNew)
Next i
End With
End Sub