Private Sub Workbook_Open()
Dim ASurveiller As Range, Fin As Date
Set ASurveiller = Intersect(Union(Range("A1:A10"), Range("C1:C10")), Cells.SpecialCells(xlCellTypeBlanks))
On Error Resume Next
While Not ASurveiller Is Nothing
If ASurveiller.Cells(1, 1).Interior.ColorIndex = 43 Then
Union(Range("A1:A10"), Range("C1:C10")).Interior.ColorIndex = -4142
Else
ASurveiller.Interior.ColorIndex = 43
End If
Set ASurveiller = Intersect(Union(Range("A1:A10"), Range("C1:C10")), Cells.SpecialCells(xlCellTypeBlanks))
Fin = Now + TimeValue("0:00:02")
While Now < Fin
DoEvents
Wend
Wend
On Error GoTo 0
End Sub