Multiply 2 columns in Matrix Table

[rsj88]

Hi

I have the below matrix table visual

		Monday	-	-	Tuesday
Vehicle Type		Quantity	Price	Cost	Quantity	Price	Cost
Vehicle Type	Car	2	2000	??? (Should be 4000)	5000	3	??? (should be 15,000)

the above data is taken from two tables. i need to add a column called Cost to multiply quantity by price?

Any ideas?

thanks