Variable as a variable name in PL/pgSQL

I'm trying to implement a sort of templates for a user database.

I tought of two possibilities. In the first I have a table like this:

CREATE TABLE templates
(
 tplname       varchar(32),
 fieldname     varchar(32),
 value         varchar(32)
);

Where I specify the value to be assigned to each field of the user's tuple.
I started writing a trigger to force the template values in the user's record
whenever it's updated or inserted. I'm using PL/pgSQL, and I'd like to continue
using it.

The function should look like the following:

CREATE FUNCTION users_trig_func() RETURNS opaque AS '
  BEGIN

    FOR row IN SELECT * FROM templates WHERE tplname = new.template;
      NEW."row.fieldname" := row.fieldvalue;
    END LOOP;

    RETURN NEW;
  END;
' LANGUAGE 'plpgsql';


Obviously the problem is the >>>NEW."row.fieldname" := expr<<< statememt.
I dont know how (if possible at all) to assign a variabile whose name is
contained in another variable, something like eval() in PHP3.

Is there a syntax or a hack ?
Whould it be hard to implement it at language level ?

Thanks in advance!

Regards.

--
 Daniele

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