How to configure automatic calculation in a column in oracle sql who's information is in another column?

I have this Fact Table:

CREATE TABLE FACTPRODUCTSALES (
    TRANSACTIONID      NUMBER
        GENERATED ALWAYS AS IDENTITY ( START WITH 1 INCREMENT BY 1 )
    PRIMARY KEY,
    SALESINVOICENUMBER INT NOT NULL,
    SALESDATEKEY       NUMBER CONSTRAINT SALES_KEY_FK REFERENCES DIMDATE (DATEKEY),
    SALESTIMEKEY       NUMBER CONSTRAINT SALESTIME_KEY_FK REFERENCES DIM_TIME (TIMEKEY),
    STOREID            NUMBER NOT NULL CONSTRAINT STORE_ID_FK REFERENCES DIMSTORES (STOREID),
    CUSTOMERID         NUMBER NOT NULL CONSTRAINT CUSTOMER_ID_FK REFERENCES DIMCUSTOMER (CUSTOMERID),
    PRODUCTID          NUMBER NOT NULL CONSTRAINT PRODUCT_ID_FK REFERENCES DIMPRODUCT (PRODUCTKEY),
    SALESPERSONID      INT NOT NULL CONSTRAINT SALESPERSON_ID_FK REFERENCES DIMSALESPERSON ( SALESPERSONID ),
    QUANTITY          FLOAT,
    SALESTOTALCOST    INT as (DIMPRODUCT.PRODUCTSALESCOST * QUANTITY),
    PRODUCTACTUALCOST INT as (DIMPRODUCT.PRODUCTACTUALCOST * QUANTITY),
    DEVIATION         FLOAT
);

As you can see in the SALESTOTALCOST and PRODUCTACTUALCOST, I want to automatically calculate their values each time I insert something on this table depending on the value inside of the DIMPRODUCT.PRODUCTSALESCOST and DIMPRODUCT.PRODUCTACTUALCOST depending on what's the ID inserted by the user in the field of DIMPRODUCT but of course, this code wouldn't work.

Is this possible?

In general, don't do that.

Either:

1. Create a VIEW and generate the totals in the view by joining the two tables.
2. If you want to materialise the data then create a MATERIALIZED VIEW.
3. Use a (compound) trigger to update the table when the dependant columns are modified.

You do not provide details of the DIMPRODUCT table or how the two tables are related so providing code is impossible.