Saveas with previous month in file name

Hi All,

Im trying to use this code with the end result being the saved file will have the previous month (2 digit) at the end of filename eg 11-Test-03.xls. Works with current month but when i try to -1 month all hell breaks loose.
Any help appreciated. thanks.

Sub saveas()
'
' saveas Macro
'

'
    ChDir "C:\Test"
    ActiveWorkbook.saveas Filename:= _
        "C:\Test\11-Test-" & Format(Now, "MM") & ".xls" _
        , FileFormat:=xlNormal, Password:="", WriteResPassword:="", _
        ReadOnlyRecommended:=False, CreateBackup:=False

End Sub