Forms 6i update row by row

Question

dear sirs,
i have form with the folllowing items
item1, item2,item_result
100 20 80
80 10 70
70 10 60
you will find that
1- item_result = item1 - item2
2- the value of item_result will go to item1 that is mean item1 is the second row = item_result
i hope when i make update in item2, item1 and item_result change depend on this update for example
if i make this update
item1, item2. item_result
100 25 75
75 10 65
65 5 60
please tell me how to do code this
thanks in advance

Answer 1

i try to change the style of asking and tell the problem maybe anybody help me and answer, but anyhow i solved myself and here is the code for people.
i made button to calculate and this the the code for event when_button_pressed
declare
     cursor c is
     select num1,NUM2,result
     from a;
     counter number(2) := 0;
     v number(5);
     v_net number(5);
begin
     for i in c loop
          v_net := 0;
     counter := counter +1;
     exit when c%notfound;
               v_net := :num1 - :num2;
          go_block('a');
          next_record;
               if :id is not null then
                    :num1 := v_net;
               end if;
          end loop;
end;