Automatically open a copy of the attached file when I open a specific message with subject on specific outlook folder

Question

I created a custom folder on outlook with name “MyTemplate” and inside that folder an email message with subject Auto Plan ( It is a template email with oft extension) ,
and inside that email an excel workbook.
For automation purpose, I need after I open that email message, then a copy of the attached workbook will be opened automatically.
I found the below code, But I cannot utilize it to fulfil my need.
Notes: for testing purpose I set outlook and excel macro security settings to “Enable all macros”.
That is my own email meassge (I fully trust) ,I also added the a personal digital certificate to the workbook and ThisOutlookSession. I am using outlook 2016 32Bit with Windows 10 64Bit.
As always, grateful for any assistance.

Public WithEvents myItem As Outlook.MailItem
Public EventsDisable as Boolean
 
Private Sub Application_ItemLoad(ByVal Item As Object)
    If EventsDisable = True Then Exit Sub
    If Item.Class = olMail Then
        Set myItem = Item
    End If
End Sub
 
Private Sub myItem_Open(Cancel As Boolean)
    EventsDisable=True
   'Your code
    EventsDisable=False
End Sub

Answer 1

1. As I tried suggesting in my comments, you should modify Outlook Macro Security Settings to 'Notifications for all macros'. Then, the session must be closed and reopen choosing Macro Enabled.

2. Copy the next code on top of the previous Sub:

Option Explicit

Public WithEvents MyItem As Outlook.MailItem
Public EventsDisable As Boolean

Private Sub Application_ItemLoad(ByVal Item As Object)
    If EventsDisable = True Then Exit Sub
    If Item.Class = olMail Then
        Set MyItem = Item
    End If
End Sub
Private Sub myItem_Open(Cancel As Boolean)
    EventsDisable = True
        If MyItem.Subject = "Auto Plan" And Application.ActiveExplorer.CurrentFolder.Name = "MyTemplate" Then
            If MyItem.Attachments.Count > 0 Then
                Dim obAttach As Attachment, strSaveMail As String, objExcel As Object
                Set obAttach = MyItem.Attachments(1)
                strSaveMail = "C:\Teste VBA Excel\outlook-attachments\"
                obAttach.SaveAsFile strSaveMail & obAttach.DisplayName
  
                Set objExcel = CreateObject("Excel.Application")
                objExcel.Workbooks.Open strSaveMail & obAttach.DisplayName
                objExcel.Visible = True: AppActivate objExcel.ActiveWindow.Caption
                Set objExcel = Nothing
            End If
        End If
    EventsDisable = False
End Sub

The Open event previously save the attachment workbook, creates an Excel session, makes it visible and open it there. It, probably, could get the existing session, but I was working there on a project and I did not dare to risk accidentally closing it...

Please, test it and send some feedback. It, probably, can be optimized, but I only tried obtaining a workable solution. It worked on my environment...