Advise user if workbook open, who is the 'owner' and option to try again

Hi,

I'm trying to adapt some code to check if a file is already open (get the name of the 'owner' and pass it back) and give the user the option to try again. I plan to create a small userform with a label caption and a button to try again - "... goto tryagain"

However, I'm failing at the first hurdle as I get a runtime error 450 on GetSecurityDescriptor in the function.

I've probably done something stupid, but can't see it - maybe because it's a Friday afternoon and I'm a bit tired...

Code in sub:

      If Dir(PymtTLPath, vbDirectory) = "" Then
            TempPTPath = Range("nrTempPTPath") 'contains filepath, allows user to ammend if need be

            Workbooks.Open fileName:=TempPTPath, Password:="xxx"
            
            If ActiveWorkbook.ReadOnly Then
                MsgBox "The file is locked by " & GetFileOwner(TempPTPath) & "."
                'code to be amended here to close the file, change message box to lable caption in a userform and give the user the option to try again
            End If

        Else
            Workbooks.Open fileName:=PymtTLPath, Password:="xxx" 'if the file already exists, open it
        End If

Code in function:

Function GetFileOwner(FilePath As String) As String

    Dim secUtil As Object
    Dim secDesc As Object

    Set secUtil = CreateObject("ADsSecurityUtility")
    Set secDesc = secUtil.GetSecurityDescriptor(FilePath)
    GetFileOwner = secDesc.owner

End Function

Anyone spot the obvious mistake?!

Thanks, TC