Creating custom fields in emails

Hello,

To help in linking Outlook emails to our task management system, I'd
like to see if it's possible to create a custom field in Outlook 2007
so I can attach a task number to each email (where one would apply
anyway). For example, if someone emails me wanting an email address
changed, I'd create a new task which would generate a task number. I
want to somehow add this to the email so I can retrieve it more
quickly in the future if ever needed.

In Outlook 2007 when I go into Customize Current View by right-
clicking on the headings, then click Fields, there is an ability to
create a New Field, which I did. I can even add this field as a
column, which works great, however I can't find anyway to add content
to or edit the field after that.

Any suggestions?

Thanks --

Alex