Private Sub Workbook_Open()
Application.OnTime 1, "ThisWorkbook.ArrierePlan" 'lance la macro
End Sub
Private Sub ArrierePlan()
'---les noms A B C D sont à adapter---
Dim w As Worksheet
Do
If ActiveSheet.Name = "A" And ActiveCell.Interior.Color = vbRed Then
For Each w In Sheets(Array("B", "C", "D"))
w.Range(ActiveCell.Address).Interior.Color = vbRed
Next
End If
DoEvents
Loop
End Sub