copy worksheet to new workbook and save as .xlsm

Hello there,

I was fortunate enough to find some code written by Joe4 which I customized just sligtly. But I am unable to save using .xlsm format.
Any ideas?
Saving .xlsx works fine.


Thanks

Sub Copy2_NewWB()


    Dim mySourceWB As Workbook
    Dim mySourceSheet As Worksheet
    Dim myDestWB As Workbook
    Dim myNewFileName As String
    Dim nSName As String
    
    sName = Range("B1")
    
    
'   First capture current workbook and worksheet
    Set mySourceWB = ActiveWorkbook
    Set mySourceSheet = ActiveSheet
    


'   Build new file name based
    myNewFileName = mySourceWB.Path & "\" & sName & ".xlsm"

'   Add new workbook and save with name of sheet from other file
    Workbooks.Add
    ActiveWorkbook.SaveAs Filename:=myNewFileName
    Set myDestWB = ActiveWorkbook
    
'   Copy over sheet from previous file
    mySourceWB.Activate
    Cells.Copy
    myDestWB.Activate
    Range("A1").Select
    ActiveSheet.Paste
    Application.CutCopyMode = False
    
'   Resave new workbook
    ActiveWorkbook.Save


End Sub

It hags on the SaveAs line with:
"Run-time error '1004' This file ext cannot be used with the selected file type. Change the file ext, etc