Material Landed cost in Purchasing

Dear ABAP/BI Experts,

We have a requirement like need to achieve material Cost Using Purchasing InfoCube and DSO Flatfile source the below conditions.

1)If the Material Cost is getting from a system(ECC) for a particular month,then the Base Price is the cost of Material Price for that month .

2)Else it has to consider the Previous month Material cost(From ECC) *Base Price change % getting from DSO(Flat file Source which is having % price change to each month for all material list) for that month.

Could you please suggest what is logic(ABAP) and what are the Infoproviders required for this using existing DSO(Flat File) and InfoCube(Standard Purchasing Groups Cube).

Regards

Venkat