Combobox values based on query

Question

I created combobox but how can I set its record source to be based on a query ?

Answer 1

Well it was no working, however I did it myself like this:
Declare
num number;
my_spid varchar2(9);
my_desc varchar2(25);
myvar varchar2(9);
i number;
BEGIN
select count(*) into num from specialty_master;
i:= 1;
loop
myvar:='SP00'||i;
SELECT description, sp_id INTO my_desc, my_spid FROM specialty_master where sp_id=myvar;
Add_List_Element('SP_ID', i, my_desc, my_spid);
i := i + 1;
exit when i > num;
end loop;
END;
My Sp_id in database was like: SP001,SP002,SP003
I had to use myvar:='SP00'||i because of some rownum problem.
But now my error is: No initial value selected for listbox.
How to set initial value.