Option Explicit
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim n As Byte, Start As Variant, i As Integer
ActiveSheet.Unprotect
If [O1] = 1 Then
For i = 1 To 10 'Nombre de flashes 10
With Range("F10:K21")
.Font.ColorIndex = 6
.Interior.ColorIndex = 3
End With
For n = 1 To 40 'Intervalle des flashes
Start = Timer
Do While Timer < Start + 1 / 100
Loop
If n Mod 20 = 0 Then 'Durée des flashes
With Range("F10:K21")
.Font.ColorIndex = 34
.Interior.ColorIndex = 41
End With
End If
Next n
Next i
End If
ActiveSheet.Protect
End Sub