Temp tables as session var containers

Hi,

I've seen the session variable question pop up a fair bit on this list.
The temporary table solution seems good but I've got a question before
using it...

- My app creates a temp table for session vars
- UPDATE, INSERT and DELETE triggers on tables use this data

My question is:

If I run a query directly through the psql command line tool (or another
app that doesn't setup this temp table) that temp table wont exist.

How can I write the trigger function to detect the absence of the temp
table and deal with it gracefully? I think I need some SQL to determine
which pg_temp_N schema belongs to my session.

Is this possible?

TIA,
James