Macro clignotement cellule qui fonctionne pas bien

Option Explicit

Private Declare Function SetTimer Lib "user32" _
                        (ByVal hWnd As Long, _
                         ByVal nIDEvent As Long, _
                         ByVal uElapse As Long, _
                         ByVal lpTimerFunc As Long) As Long

Private Declare Function KillTimer Lib "user32" _
                        (ByVal hWnd As Long, _
                         ByVal nIDEvent As Long) As Long

Private m_TimerID As Long

'Note:  The duration is measured in milliseconds.
'         1,000 milliseconds = 1 second
Public Sub StartTimer(ByVal Duration As Long)
  'If the timer isn't already running, start it.
  If m_TimerID = 0 Then
    If Duration > 0 Then
      m_TimerID = SetTimer(0, 0, Duration, AddressOf TimerEvent)
      If m_TimerID = 0 Then
        MsgBox "Timer initialization failed!"
      End If
    Else
      MsgBox "The duration must be greater than zero."
    End If
  Else
    MsgBox "Timer already started."
  End If
End Sub

Public Sub StopTimer()
  'If the timer is already running, shut it off.
  If m_TimerID <> 0 Then
    KillTimer 0, m_TimerID
    m_TimerID = 0
  Else
    MsgBox "Timer is not active."
  End If
End Sub

Public Property Get TimerIsActive() As Boolean
  'A non-zero timer ID indicates that it's turned on.
  TimerIsActive = (m_TimerID <> 0)
End Property

Private Sub TimerEvent()
  Debug.Print "Timer event fired: "; Format$(Now, "long time")
End Sub

Private Declare Function SetTimer Lib "user32" _
                        (ByVal hWnd As Long, _
                         ByVal nIDEvent As Long, _
                         ByVal uElapse As Long, _
                         ByVal lpTimerFunc As Long) As Long
Private Declare Function KillTimer Lib "user32" _
                        (ByVal hWnd As Long, _
                         ByVal nIDEvent As Long) As Long
Private m_TimerID As Long, m_fin As Date

Private Sub Blink()
Dim xCell As Range
Set xCell = Range("F2")

With ThisWorkbook.Worksheets("Feuil1").Range("F2").Font
    If xCell.Font.Color = vbRed Then
        xCell.Font.Color = vbWhite
  Else
        xCell.Font.Color = vbRed
    End If
End With

If Now > m_fin Then
    Call StopBlink                                             
End If
End Sub

Public Sub StartBlink()
Dim Duration As Long: Dim Duree As Long
Duration = 100
Duree = 10                       

'Fréquence de clignotement, en millisecondes et Durée du clignotement, en secondes
                                                                      
m_fin = Now + TimeSerial(0, 0, Duree)
If m_TimerID = 0 Then
    If Duration > 0 Then
      m_TimerID = SetTimer(0, 0, Duration, AddressOf Blink)
      If m_TimerID = 0 Then
        MsgBox "Echec de l'initialisation du minuteur."
      End If
    Else
        MsgBox "La durée doit être supérieure à zéro."
    End If
  Else
        MsgBox "Timer déja démarré."
  End If
End Sub

Public Sub StopBlink()
  If m_TimerID <> 0 Then
     KillTimer 0, m_TimerID
     m_TimerID = 0
  Else
    MsgBox "Timer non actif."
  End If
End Sub

If Now > m_fin Then
    Unload UserForm1               'Ferme l'USF1
    Call StopBlink

End If
End Sub

Public Sub StartBlink()
Dim Duration As Long: Dim Duree As Long
Duration = 100: Duree = 10
    
    UserForm1.Show 0                                   'Ouvre l'USF1

m_fin = Now + TimeSerial(0, 0, Duree)
If m_TimerID = 0 Then
    If Duration > 0 Then