Help with function

I am trying to write a very generic function to be used for table auditing. I am kind of stuck on how to make the function use the column names I pull from the db. Is there anyway to do what I have below? My main concern is this segment:

if (new.columnName != old.columnName or
(old.columnName is null and new.columnName is not null) or
(old.columnName is not null and new.columnName is null)
) then

How can I get PostgreSQL to substitute the selected column name for the old.columnName/new.columnName?

Thanks,

Chris

CREATE OR REPLACE FUNCTION table_update_trig_func() RETURNS "trigger" AS
'
declare
/* setup the local variables */
loopRec record;
columnName varchar;
sqlStr varchar(2000);
begin
/* write out to the log file where we are */
raise notice \'in start of table_update_trig_func\';

/* setup the current sql string */
sqlStr := \'select attname as columnName \';
sqlStr := sqlStr || \'from pg_class, pg_attribute, pg_type \';
sqlStr := sqlStr || \'where pg_class.relname = \'\'table\'\' \';
sqlStr := sqlStr || \'and pg_attribute.attrelid = pg_class.oid \';
sqlStr := sqlStr || \'and pg_attribute.atttypid = pg_type.oid \';
sqlStr := sqlStr || \'and pg_type.typname not in (\'\'oid\'\',\'\'tid\'\',\'\'xid\'\',\'\'cid\'\',\'\'oidvector\'\') \';
sqlstr := sqlStr || \'order by attname \';

/* start the check of each column in the table */
for loopRec in execute sqlStr loop

raise notice \'value of loopRec.columnName is %\', loopRec.columnName;

columnName := loopRec.columnName;

if (new.columnName != old.columnName or
(old.columnName is null and new.columnName is not null) or
(old.columnName is not null and new.columnName is null)
) then

raise notice \'table_update_trig_func - calling insert_into_log function\';

select * from eedi.insert_into_clmchglog(<parameters>);

end if;

end loop;

return new;

end;
'
LANGUAGE 'plpgsql' STABLE SECURITY DEFINER;