Thanks for your reply.
I want to create a custom tag but only want to use it under varying conditions. For example, it may be by usergroup or after a member reaches a certain number of posts, etc.
If I knew 1 location where I can 'unset' that custom tag from the $tag_list array based on one or both conditions previously mentioned, or find that function that nearly all message code regardless of the application (forum, pm, etc.) and strip out that custom tag, then that would be a great help.
Thanks again, in advance.
EDIT: Answer:
http://www.vbulletin.com/forum/showthread.php?t=152002