Short answer: Yes.
Longer answer: You can add files to the "Attachment_Name" parameter, I don't have the exact syntax in my head but with some debugging this should be to hard to figure out, if my memory serves me correctly each entry is a filename/url pair, when pointing the url-part to a local file it will be uploaded.
I've done this myself when pasting Word documents into an WYSIWYG-editor to get linked images to upload automatically.
Best regards,
// Patrik