Make Trigger run after completion of ENTIRE transaction

This maybe more of a theoretical question, can you actually make a Trigger
run
after completion of the entire transaction?

Here's what I have:
LOG
user | startdate | enddate

enddate is getting updated by a trigger (on insert or update).

I have the following transaction:
BEGIN;
Insert into LOG(user,startdate) values('jdoe','2006-08-13');
Insert into LOG(user,startdate) values('jdoe','2006-08-14'); Insert into
LOG(user,startdate) values('jdoe','2006-08-15'); Insert into
LOG(user,startdate) values('jdoe','2006-08-16'); Insert into
LOG(user,startdate) values('jdoe','2006-08-17');
........... *another 20-30 more inserts..........*
COMMIT;

The trigger actually runs on each Insert and therefore slows down the
Insert quite a bit.

My question is, can you tell the trigger to run after Commit?