LOV Help

Hi,,
I have given a task to create an LOV using codes in pl/sql editor,,
I have creatd a text item and I want to display the lov in it..
I used the trigger when new form instance and my code is:


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declare
rg_name VARCHAR2(40) := 'pid_rg';
rg_id RecordGroup;
list_id item;
lov_id LOV;
x boolean;
begin
rg_id := Find_Group( rg_name );
IF Id_Null(rg_id) THEN
rg_id:=create_group_from_query(rg_name,'select patientid from register');
	IF Id_Null(rg_id) THEN
     Message('Create group failed');
     Message(' ',no_acknowledge);
     Raise Form_trigger_failure;
	End if;
	end if;
	:id_lov.error:=populate_group(rg_id);
	lov_id:= Find_LOV('pid_lov');
	SET_LOV_PROPERTY(lov_id,group_name,rg_name);
	set_item_property('id_lov.idd',lov_name,'pid_lov');


end ;

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whenever i run it I get an error that the record group and LOV do not exist,,I need your help please..
I also have a question: do I need to create the LOV manually in the object navigator
but without data first??this what i have did and it did not work!!!