Select multiple values in mult-select list

Question

I have the following query as the source for a multi-select page item:
SELECT person.person_id
FROM person, pers_proj_task
WHERE pers_proj_task.person_id = person.person_id
AND pers_proj_task.project_id = :P3_PROJECT_ID
The query returns two records and the page item's session value is 4:3, but only the value 4 is highlighted in the mulit-select list. How can I get both values to be highlighted?

Answer 1

Got it to work for a multi-select item by following Dimitri's post which uses a shuttle example. It was still only highlighting one value, but I tried Patrick Wolf's suggestion from the comments on Dimitri's post to put the pl/sql block in the source of the item rather than as a computation and it worked.
So I now have a multi-select list which has default values pulled from a LOV. The items that are highlighted by default are selected by using the following pl/sql block in the "source/value or expression" of the :P3_PERSON_ID multi-select item:
declare
person_list apex_application_global.vc_arr2;
i number := 1;
begin
for r in ( SELECT person.person_id
FROM person, pers_proj_task
WHERE pers_proj_task.person_id = person.person_id
AND pers_proj_task.project_id = :P3_PROJECT_ID)
loop
person_list(i) := r.person_id;
i := i + 1;
end loop;
return APEX_UTIL.TABLE_TO_STRING(person_list,':');
end;
Thanks to Amanda, ArtS, Dimitri and Patrick.
Jeremy