Attachment using select dropdown

Hi,

I’m trying to send an auto-response email with a local file attachment. I want to send the attachment according to the option selected in a dropdown.
Here’s how I’m trying to do it:

[select your-attachment "File 1|uploads/2014/04/04/file1.pdf" "File 2|uploads/2014/04/04/file2.pdf"]

And then in the File attachments field: [your-attachment]

However, this isn’t working.
Any ideas of how can I make it work?

Thanks

https://wordpress.org/plugins/contact-form-7/