SQL & PL/SQL

Hi,

i have 2 tables
1-item

2-store

and i made a many to many relationship between them so i created the third table (item_store) and it has 3 columns (item_code, store_code, quantity)

now i want to get the total number of (current_stock) column which in (item) table for a specific item_code

example;  item_store  table

item_code    store_code    quantity

  1                      1               100

  1                      2               100

so when i go to table item.current_stock  it should be 200

i'll be grateful if any one told me how to do that

Thanks