Configuration steps for Material Cost estimation with quota arrangement value

Example:

A supplier = 70% RM 1.00 = RM 0.70

B supplier = 30% RM 0.70 = RM 0.21

Total Allocation price approval from vendor is RM 0.91

But when System capture last PO Price for Costing, let say we receive goods from Supplier A that price is RM 1.00, this is totally wrong pickup. Got any solution for this?