title: "Argument not optional" error when running sub
body: <p>When I try to run a sub (below), I get the compile error: argument not optional, at the line <code>Set wb = getDensityTemplate()</code>.  Can anyone explain this to me?  Thanks Thomas Inzina for providing this code for me.</p>
  
  <pre><code>Public Sub MultipleParts()
  Dim vFiles As Variant, FileFullName As Variant
  Dim NextRow As Range, wb As Workbook
  Dim CalculationMode As XlCalculation
  CalculationMode = ToggleEvents(False, xlCalculationManual)
  
  vFiles = getFileList("C:\Users\OneDrive-CoorsTek\temp", "*.xls*")
  If UBound(vFiles) = -1 Then
      MsgBox "No files found", vbInformation, ""
      Exit Sub
  End If
  
  Set wb = getDensityTemplate()
  
  For Each FileFullName In vFiles
      With wb.Worksheets(1)
          'Add Header
          .Range("A1:H1").Value = Array("FileName", "Description", "WaterTemp(C)", "WaterDensity(g/cc)", "PartID", "DryMass(g)", "SuspendedMass(g)", "Density(g/cc)")
          'Target the next empty row
          Set NextRow = .Range("A" &amp; .Rows.Count).End(xlUp).Offset(1)
          AddBatchCard CStr(FileFullName), NextRow
      End With
  Next
  
  ToggleEvents True, CalculationMode 
  End Sub
  </code></pre>
  
  <p>The <code>getDensityTemplate</code> sub is also shown.  </p>
  
  <pre><code>Private Function getDensityTemplate(FilePath As String) As Workbook
  Dim SheetsInNewWorkbook As Integer
  Dim wb As Workbook
  SheetsInNewWorkbook = Application.SheetsInNewWorkbook
  Application.SheetsInNewWorkbook = 1
  
  Set wb = Workbooks.Add(xlWBATWorksheet)
  wb.Worksheets(1).Name = "Density"
  wb.SaveAs FileName:=FilePath &amp; "DensitySummary" &amp; Format(Now, "yyyy_mm_dd_hh.mm")
  Set getDensityTemplate = wb
  </code></pre>
  
  <p>End Function</p>