title: =INDEX(PeriodList,MonthNo) creating _xlfn.SINGLE name in workbook
body: <p>I hope someone will be able to help with a problem that has surfaced with a recent Excel update.</p>
  
  <p>If I define two range names in an Excel worksheet and then enter =Index(PeriodList,MonthNo) in cell A13 via the UI, I find that Thisworkbook.Names.Count in VBA reports 2 - as expected. However, if I execute Activesheet.Range("A13").Formula = "=Index(PeriodList,MonthNo)" in VBA, Thisworkbook.Names.Count reports 3 and I find that a new name that cannot be deleted is created. The name is _xlfn.SINGLE. The existence of this name is a problem for a significant number of widely distributed Excel templates that fail when attempting to delete this name. This only became a problem after a recent Excel update. </p>
  
  <p>The problem seems to be with the MonthNo element in that "=Index(PeriodList,1)" does not generate the _xlfn.SINGLE name.</p>
  
  <p>Can anyone identify how to enter something that is the equivalent of "=Index(PeriodList,MonthNo)" in VBA without creating the unwelcome _xlfn.SINGLE name?</p>