Send Workbook as Attachment

Hi Gurus,

I have a workbook that needs to be sent as attachment on the click of a button but the following section of the code that caters for this macro gives me error on some of the computers in the office, and completely fine on others. The error is "TempWB.FullName = <Object variable or With block variable not set>". Here is the section that should get you into context:

'House Keeping
    Dim oApp As Object
    Dim oMail As Object
    Dim TempFilePath As String
    Dim TempWB As Workbook

    Application.ScreenUpdating = False

'Enter Read Mode
    Call EnterReadMode
     
'Create a new temporary folder on M: drive and save attachment there
    On Error Resume Next
    MkDir "M:\User Admin"
    TempFilePath = "M:\User Admin\"
    ActiveWorkbook.SaveCopyAs TempFilePath & strAttachmentName
    Set TempWB = Workbooks.Open(TempFilePath & strAttachmentName)
    On Error GoTo 0
    
'Create and send the outlook mail item

    If Worksheets("Approval").Range("E13") = "" Then
    
        Set oApp = CreateObject("Outlook.Application")
        Set oMail = oApp.CreateItem(0)
        With oMail
            .To = strApprover
            .Subject = "User Administration Approval Required"
            .Attachments.Add TempWB.FullName
            .Body = "Dear " & strApprover & "," & vbCrLf & vbCrLf _
                & "There is a user administrative request that requires your approval. " _
                & "Please see the attached User Admin Form." & vbCrLf & vbCrLf _
                & "Regards," & vbCrLf _
                & strSender
            .Display
        End With
End If

Can you help?
Thanks guys.