Is there a possibility of acquiring the item and/or journal entry while inside the trigger?
if not: Write an on entry script for the trigger that checks the journal and item ownership.
If it's only possible to acquire the item while in the trigger: Write an item on acquire script that uses the GetFirstSubArea/GetNextSubArea loop to check whether you're in the trigger.
If it's only possible to get the journal entry while in the trigger: Same thing as above but hook on to the initial journal entry.
If there are too many possibilities to use the above: Write one script that checks the journal entry and item, and use it in the trigger's heartbeat. If you prefer an instant method, write a single script that checks for the trigger (using the sub area loop), the journal entry, and the item, and have it run on the item acquire, on the trigger entry, and on the journal update. That way you're sure to hit it instantly when the conditions are met.