I put the following code into "When_New_Form_Instance" at Module level but its not working.

DECLARE
UN VARCHAR2(80);
PW VARCHAR2(80);
CN VARCHAR2(80);

BEGIN
UN := GET_APPLICATION_PROPERTY(USERNAME);
PW := GET_APPLICATION_PROPERTY(PASSWORD);
CN := GET_APPLICATION_PROPERTY(CONNECT_STRING);

if UN = 'Peter' then
set_item_property('BlockName.ItemName',visible,property_false);
END IF;
END;


Whats wrong with that code. Where should i put it?
Why GET_APPLICATION_PROPERTY(USERNAME) is not working (can't get a username)?

Any help please?
Thank you.