How can we reallocate costs at the time of PO receipt in a perpetual average cost system?

Summary:

We are using perpetual average cost.

Scenario for us is:

There are two items which we are procuring (main item and accessory item). Price of main item is 150 and accessory item is 0 on purchase order.

Our expectation is at the time of receiving we want to split the costing of these two items into 100 and 50 dollars each.

Without changing the price on purchase order. Because these lines will be used for receipt and invoice matching process.

Is there any way we can update the cost of accessory item as 50 from 0 dollars and cost of main item to 100 from 150 dollars while receiving?