After using this code to create a worksheet for each month of the year in an
existing workbook and saving it,

Sub AddSheets()
Dim sh As Worksheet
Dim i As Long

With ActiveWorkbook

Set sh = ActiveSheet
For i = 1 To 12
sh.Copy After:=.Worksheets(.Worksheets.Count)
ActiveSheet.Name = Format(DateSerial(Year(Date), i, 1), "mmmm")
Next i
End With
End Sub

Saving it created a new workbook with the same name but the extension .xlsm
and the Excel icon has a yellow overlay with an exclamation mark. Does this
mean that something is wrong with the workbook?