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?