accumulation based on two dimension

[nizamsha]

This is my table

    Date, Properties, Value

    11/12/12, Fridge, 20

    11/12/12, A/c, 30

    12/12/12, Fridge, 30

    12/12/12, A/c, 40

    12/12/12, TV, 60

    13/12/12, Fridge, 70

    13/12/12, LCD, 40

i used straight table in that i took date and properties  as dimension value as expression

Date, Properties, Value,result

    11/12/12, Fridge, 20,20

    11/12/12, A/c, 30,30

    12/12/12, Fridge, 30,50

    12/12/12, A/c, 40,70

    12/12/12, TV, 60,60

    13/12/12, Fridge, 70,120

    13/12/12, LCD, 40,40

my result should look like this