Adding a serial (or tracking) number to a from.

OK, i'm pretty noobie with outlook... All I did was to create a form (work
order) on word, copied it to a new message and save the file as a "Outlook
Template". Then, I just saved it on the server and put a link to it on the
intranet, so the users can lick on it, then the template comes up and they
can use it.
All this works pretty good, until I needed a way to track the message
(numberwise). The user has to fill it up, send it to me (maintenance), and I
assign it to a tech. But if there is not number on the form, it is kind of
hard to track it.

Any ideas on how to add a number to the e-mail. Thanks