'Boucle seulement sur les cellules concernees
Sub test()
With Worksheets("Feuil1")
Nb = Application.CountIf(.Columns(1), "*&*") 'nombre de fois
If Nb > 0 Then
lig = 1
For n = 1 To Nb
.Range(.Columns(1).Find("*&*", .Cells(lig, 1), , xlWhole).Address) = Replace(.Range(.Columns(1).Find("*&*", .Cells(lig, 1), , xlWhole).Address), "&", "et") 'remplacement
Next n
End If
End With
End Sub