Hello again, the formula should read:

=IF(J11="","",-(C11*J11)+(L11*J11))

But the result is still correct, being the £38.

I am seeing what we would have yielded at nominal price, and comparing it to our actual sales values.

I sold Product 5 @ £1,500/tonne, and should have sold it at £1,875/tonne. That's an unfavourable result of £375/tonne, but I only sold 0.1 of a tonne, so it's £37.50 negative.

I hope that helps.
Thank you.