Execute a string of command in sql'script

Hi all,
 I'm using PostgreSQL 7.0.2 on RedHat 6.0.

 I compose a SQL command string with function below :


 CREATE FUNCTION bdrm_copy(text, text) RETURNS text AS '

  DECLARE
   baseact  ALIAS FOR $1;
   namefich ALIAS FOR $2;
   path0 TEXT;
   path1 TEXT;
   path2 TEXT;
   path3 TEXT;
  BEGIN
   SELECT INTO path0 CAST(ig_tempo AS TEXT)
   FROM ti_bdrm
   WHERE ig_base = baseact;
   path0  := trim(path0) || trim(namefich);
   path1 := ''COPY ttx_window7 TO \'\''';
   path2 := path1 || path0;
   path3 := ''\'\''';
   path0  := path2 || path3 || '';'';
   RETURN path0 ;
  END;'
 LANGUAGE 'plpgsql';


 the result of :

 SELECT bdrm_copy('MOHO99', 'test2.txt') AS my_command_string;

 is :

                my_command_string
 -----------------------------------------------
  COPY ttx_window7 TO '/db/bdrm/out/test2.txt';


 Is it possible to execute this line of command? More generally, can one
 execute the contents of a variable or a field in postgresql' script?

Thanks ;)-