use of %TYPE

Can I use %TYPE in a function definition a la:
=============================================================================
CREATE OR REPLACE FUNCTION add_usr ( Usrs.first_name%TYPE,
                                     Usrs.middle_name%TYPE,
                                     Usrs.sur_name%TYPE,
                                     Usrs.sur_name_extra%TYPE,
                                     Gens.gen%TYPE,
                                     Emails.email%TYPE,
                                     UsrEmailTypes.usr_email_type%TYPE )
RETURNS BOOLEAN AS '
    DECLARE
    var_first_name      ALIAS FOR $1;
    var_middle_name     ALIAS FOR $2;
    var_sur_name        ALIAS FOR $3;
    var_sur_name_extra  ALIAS FOR $4;
    var_gen             ALIAS FOR $5;
    var_email_addr      ALIAS FOR $6;
    var_email_addr_type ALIAS FOR $7;
    BEGIN
        RETURN ''f'';
    END;
' LANGUAGE 'plpgsql';

=============================================================================

Also, does pgsql keep case in the table and column names? phpPgAdmin shows no case on tables I
created with case.