Ok, I got it working on testing to see if they have an item, I wanna make it so that if a player has the item the npc will not give the player another item. How do I do that?
just set the NoTriggerOnCarried string to refer to that item if you dont want the npc to respond at all.
If you just want to block the specific .npc dialog entry that gives out the item, just add a test like this to the Condition field
~GETONCARRIED,Helm of Power,platehelm,visible=true
which would be true whenever the item was either not visible, or not found at all.