A coworker who has 3 kids all 22 months apart gave me this idea, and it has been a winner!  I put together a very special basket for A with brand new exciting toys…however, the basket is only able to come out when I am feeding/tending to baby.  I decorated it and made a big deal about it, and A ended up learning that he can get the basket out when he sees me holding C.  Of course it is not perfect, and sometimes no amount of exciting toys can make a young toddler be patient while mom is feeding the baby, but for the most part it is an awesome tool to use!