You would set the NoTriggerOnCarried on the spawner (or npc XmlDialog) to
Blackthorn,1which tells it NOT to trigger if you are carrying the questholder named "Blackthorn" with objective 1 completed.
If you were to set TriggerOnCarried property to
Blackthorn,1
then it would only trigger if you were carrying the questholder named "Blackthorn" and had objective 1 already completed.
This is one way to set up objectives that depend on completion of other objectives first.
Note that you can also specify more than one required objective in the Trig/NoTrig properties, like
Blackthorn,1,3,4
would tell it to check for the Blackthorn questholder with objectives 1,3, and 4 completed.
check this thread for more info on using Trig/NoTrigOnCarried
http://xmlspawner.15.forumer.com/index.php?showtopic=28