Email Inbox Filters

I'm trying to set up a system that will automatically send an email with correct formatting to be entered into our Altiris Helpdesk Ticketing system and autopopulate the correct fields.  Unfortunately the information given in the manual is sparce on this topic.  I dug around in the formats.xml file and found what I believe are the correct values for the fields I want to populate, but am unsure of what values to enter.  I want to have the data in the email force the correct Category (and subcategory, if applicable) upon ticket creation.  So far, I have:

{HelpdeskData}

{HelpdeskValue} workitem_category_lookup_id = ??????? {/HelpdeskValue}

{HelpdeskValue} workitem_category_tree_value = ???????? {/HelpdeskValue}

{/HelpdeskData}

Anything I've tried putting in for values hasn't worked so far.  Unfortunately, there are no integers associated with the Categories List in the Administrator tab, and the categories don't appear in the Lookups module.  Am I missing anything?

Thanks