title: Excel macro vlookup R1C1 perfomance issue
body: <p>I am working on a macro in which I have to compare two string values. 
  I have used vlookup to manage this and though I can see it takes up a lot of resources it has been working quite well. Until this week. 
  The resources go to full and Excel freezes. If I cancel the action with esc it occasionally gives the error 1004 autofill method of range class failed. Other times it seems the action is finished, I see the result of the compare and it accepts the hard stop. I use the following code.</p>
  
  <pre><code>Sub combineMessageDataCLFArchi()
  Application.ScreenUpdating = False
  
  Worksheets("clf_import").Range("F1").FormulaR1C1 = "=IFERROR(VLOOKUP(RC[-4],archi_relations!C[-5]:C[-1],3,FALSE),0)"
  Range("F1").Select
  Selection.AutoFill Destination:=Range("F:F")
  
  Worksheets("clf_import").Range("G1").FormulaR1C1 = "=IFERROR(VLOOKUP(RC[-5],archi_relations!C[-6]:C[-2],5,FALSE),0)"
  Range("G1").Select
  Selection.AutoFill Destination:=Range("G:G")
  
  Application.ScreenUpdating = True
  
  End Sub
  </code></pre>
  
  <p>There were no changes made to the code prior to me looking for a solution. 
  I have tried to just run one of the lookups but that gives the same result. 
  I have tried to return a TRUE but had the same result.
  I have tried to do the double vlookup perfomance hack but did not manage to make it work. 
  If the error is thrown it is thrown on Selection.AutoFill Destination:=Range("G:G")</p>