Customize virtuemart from unit to size

1 On Product: change unit to size (250gr 500gr 1kg 1.5kg 2.5kg) (not for all product) pictures 1 2 Add setting on backend (this for all product) pictures 2 3 On cart show change unit to size and change price automatic pictures 3 4 Category change the price on kg (not for all product) pictures 4 3 When the user change size the price have to change in automatic (this for all product) pictures 5