Public RunWhen As Double
Sub StartBlink()
With ThisWorkbook.Worksheets("Sheet1").Range("A1").Font
If .ColorIndex = 3 Then ' Red Text
.ColorIndex = 2 ' White Text
Else
.ColorIndex = 3 ' Red Text
End If
End With
RunWhen = Now + TimeSerial(0,0,1)
Application.OnTime RunWhen, "'" & ThisWorkbook.Name & "'!StartBlink", , True
End Sub
Sub StopBlink()
ThisWorkbook.Worksheets("Sheet1").Range("A1").Font.ColorIndex = _
xlColorIndexAutomatic
Application.OnTime RunWhen, "'" & ThisWorkbook.Name & "'!StartBlink", , False
End Sub
Then, in the ThisWorkbook code module of the workbook, use code like:
Private Sub Workbook_Open()
StartBlink
End Sub
Private Sub Workbook_BeforeClose(Cancel As Boolean)
StopBlink
End Sub