Oracle Forms

Hi,

Knows someone how can I use dbms_output.put_line in oracle forms?
I wrote on "when the button pressed" the following:
DECLARE
CURSOR c_firme IS select codfirma, denfirma, loc from firme where zona='BANAT';

BEGIN
DBMS_OUTPUT.PUT_LINE('Lista cu firmele din Banat: ');

FOR rec_firme IN c_firme LOOP
DBMS_OUTPUT.PUT_LINE('Firma ' ||rec_firme.denfirma|| ' este din localitatea: '||rec_firme.loc);
END LOOP;
END;

but I have no results.
In Sql I have the results.

Thank you