Stored Proc Problem

[Robert Landrum <rlandrum(at)aol(dot)net>]

I'm writing a stored procedure that will execute as a trigger. 
Arguments being passed to the procedure are field names.

My goal is to convert those field names into the field values.  However, 
I've not been successful.  I thought that the following should have worked.

EXECUTE ''field_val := NEW.''||tg_argv[1]||'';'';

Nor does

EXECUTE ''SELECT INTO field_val NEW.''||tg_argv[1]||'';'';

I've tried using open for execute too...  No luck.

Is this possible in pure SQL?

Rob