Drop this code all under "ThisWorkbook" in VBAProject window. Change anything in bold to fit your spreadsheet. This will actually flash yellow - change 6's to 3's if you want Red
Private NextFlash As Double
Private Const FR As String = "'
[Name Of Your Workbook.xls]Name Of Your Sheet'!A3"
Sub StartFlashing()
If Range(FR).Interior.ColorIndex =
6 Then
Range(FR).Interior.ColorIndex = xlColorIndexNone
Else
Range(FR).Interior.ColorIndex =
6
End If
NextFlash = Now + TimeSerial(0, 0, 1)
Application.OnTime NextFlash, "ThisWorkbook.StartFlashing", , True
End Sub
Sub StopFlashing()
Range(FR).Interior.ColorIndex = xlColorIndexNone
Application.OnTime NextFlash, "ThisWorkbook.StartFlashing", , False
End Sub
Private Sub Workbook_Open()
ThisWorkbook.StartFlashing
End Sub
Private Sub Workbook_Close()
ThisWorkbook.StopFlashing
End Sub