G'day Keith

Try this and see how you go, it is a modified version of a code I use to
Mail/SaveAs "less the (Mail) part of the code"

Sub SaveMy_ActiveWB()
Dim FileExtStr As String
Dim FileFormatNum As Long
Dim SourceWB As Workbook
Dim MyFilePath As String
Dim MyFileName As String

Set SourceWB = ActiveWorkbook

With SourceWB
If Val(Application.Version) < 12 Then
FileExtStr = ".xls": FileFormatNum = -4143
Else
Select Case SourceWB.FileFormat
Case 51: FileExtStr = ".xlsx": FileFormatNum = 51
Case 52:
If .HasVBProject Then
FileExtStr = ".xlsm": FileFormatNum = 52
Else
FileExtStr = ".xlsx": FileFormatNum = 51
End If
Case 56: FileExtStr = ".xls": FileFormatNum = 56
Case Else: FileExtStr = ".xlsb": FileFormatNum = 50
End Select
End If
End If
End With

MyFilePath = Environ$("C:\My Documents") & "\"
MyFileName = Sourcewb.Name & " " & Format(Now, "yyyymmdd h-mm")

With SourceWB
.SaveAs MyFilePath & MyFileName & FileExtStr,
FileFormat:=FileFormatNum
End With
End Sub

HTH
Mark