I need to include in an email a hyperlink that will open an appointment
request in the recipient's calendar.  Is there an Mailto: equivalent for
appointments?

(If you're wondering why I don't just send the appointment request instead
of an email with a link inside is because I'm using a SharePoint workflow and
the workflow only give me the option of sending emails and not meeting
requests - I think).  

Thanks in advance, Dozzee