Attaching tracking/project numbers to email messages?

We use a trouble ticket/project tracking application at work. I was wondering if there is an easy way to configure some sort of custom menu or command that would allow me to easily attach or associate an email message with a 4-digit project ticket number? I'm using Outlook 2002.

Right now, I'm just editing the email message and adding the 4 digit number to the end of the subject line.

I guess what I was imagining was having the typical files, i.e. attachment, importance, flag, subject, date received...but then have an extra filed called "Ticket" or something, and I could group email messages on that field.