Option Explicit
Public Inter As Range, affiche As Boolean, t#
Sub Clignote()
If Inter Is Nothing Then Exit Sub
affiche = Not affiche
Inter.FormatConditions(1).Font.ColorIndex = IIf(affiche, 2, 53) 'blanc puis brun
t = Now + 1 / 86400
Application.OnTime t, "Clignote"
End Sub