To create a blinking cell:
If you define a new Style (Format / Style / Flash/ Add ) and apply that style to the cells you want to flash, paste the following code into a module sheet and run the procedure Flash from Auto-Open if desired you will get the text flashing alternately white and red.
Dim NextTime As Date
Sub Flash()
NextTime = Now + TimeValue("00:00:01"

With ActiveWorkbook.Styles("Flash"

.Font
If .ColorIndex = 2 Then .ColorIndex = 3 Else .ColorIndex = 2
End With
Application.OnTime NextTime, "Flash"
End Sub
Sub StopIt()
Application.OnTime NextTime, "Flash", schedule:=False
ActiveWorkbook.Styles("Flash"

.Font.ColorIndex = xlAutomatic
End Sub