discount based on quantity in the cart

[bonbin]

hi all

is it possible to create a discount based on the quantity in the cart
it doesnt matter what items same or different items still can get the discount

for example lets say im selling 4 kind of items which is A,B,C,D each items have a different price
A=$7
B=$8
C=$9
D=$10
i want to set the discount buy 2 items get discount $1 for each items, buy 3 items discount $2 for each items

so if the customers buy A & B they will get a discount $1 for each items
A:$7-$1=$6
B:$8-$1=$7

if the customers buy A, B ,& C they will get a $2 discount for each items
A:$7-$1=$5
B:$8-$1=$6
C:$9-$2=$7

Or if they bought the same items like A+C+C they will also get a $2 discount for each items
A:$7-$1=$5
C:$9-$2=$7
C:$9-$2=$7

im searching the forum already but end up with no luck
pls help

thx

[bonbin]

any help?

i need to find out which plugins or 3rd extension that might have this feature

thx