Option Explicit
Public counter As Range
Sub Start_Timer()
Set counter = Sheets("Feuil1").Range("b2")
Application.OnTime Now + TimeValue("00:00:01"), "CaR"
End Sub
Sub CaR()
Start_Timer
counter = counter - TimeValue("00:00:01")
If counter = 0 Then Application.OnTime Now + TimeValue("00:00:01"), "CaR", , False: _
counter = TimeSerial(0, 0, 10) 'change ici le temps identique à B2
End Sub