Determine if type of trigger operation (CREATE or UPDATE)

I'm trying to create a WorkFlow that can MAYBE accomplish something I have not been able to accomplish with saved search email notifications.  Basically I need to alert the Assignee of a Task when a task is created OR when the assignee is changed.  I started with a WorkFlow triggering on CREATE and UPDATE.  I then tried to build some conditions to filter on either:
[LIST]
[*]Assignee changing from empty to not empty ("create")
[*]Assignee changing from "joe" to "mary" ("update")[/LIST]I had trouble doing this so then though I would maybe create two States for update and create and break my logic into two states.  I quickly realized that I couldn't find a way to determine if my workflow was in a Create context or update context.  Internal ID is not exposed so I can't check for that being empty...