Hello,
Attached my macro that worked for me. Thank you for your help.
Private Sub Workbook_Open()
'Checks if the file is an attachment to a email
If InStr(1, ThisWorkbook.FullName, "Temporary") > 0 Then
update_macro
End If
End Sub
Sub update_macro()
Set xlobj = CreateObject("Scripting.FileSystemObject")
UserName = Environ("USERNAME")
path_addin = "C:\Documents and Settings\" & UserName & "\Application Data\Microsoft\AddIns\"
addin_file = Application.VBE.ActiveVBProject.Filename
AddIns("Makros").Installed = False
On Error Resume Next
Kill (path_addin & "MyMacro.xlam")
On Error GoTo 0
xlobj.CopyFile addin_file, path_addin & "MyMacro.xlam"
AddIns("Makros").Installed = True
MsgBox "New macro installed in " & Polku
ActiveWorkbook.Saved = True
Application.Quit
End Sub