Exemple Find de Microsoft message erreur

Sub Test()
Dim c As Range
With Sheets("Feuil1").Range("B:B")
    Set c = .Find("Phoenix", , xlValues, xlWhole, , , False)
    If Not c Is Nothing Then
        Do
            c.Value = 5
            Set c = .FindNext(c)
        Loop While Not c Is Nothing
    End If
End With
End Sub

Sub Test()
Dim c As Range
With Sheets("Feuil1").Range("B:B")
    Set c = .Find("Phoenix", , xlValues, xlWhole, , , False)
    If Not c Is Nothing Then
        Do
            c.Value = 5
c.Offset(0, 2).Value = "trouvé et remplacé"
            Set c = .FindNext(c)
        Loop While Not c Is Nothing
    End If
End With
End Sub

test

Sub Trouver_Occurences_Boucle()
Dim C As Range
Dim firstAddress$
With Worksheets(1).Range("B:B")
  Set C = .Find("Phoenix", LookIn:=xlValues)
  If Not C Is Nothing Then
    firstAddress = C.Address
    Do
      C.Value = 5
      Set C = .FindNext(C)
      
[COLOR="Blue"]      '--- Si C Is Nothing on ne peut pas exécuter l'instruction C.Address
      '--- qui déclenche l'erreur 91
      '--- Pour y remédier, il suffit de réaffecter la 1ère cellule valide à C
      If C Is Nothing Then Set C = Range(firstAddress)
      '-------------------------------------------------[/COLOR]
    
    Loop While Not C Is Nothing And C.Address <> firstAddress
  End If
End With
End Sub