Price per litre

[Bmm_beer]

Hi, we have a beer store where volume of the products are displayed in a custom field in centilitres and liters.

We'd need to display, besides salesprice, price per litre, as in the attached photo.

I can see no option in Virtuemart and I don't know how can I customize this. Can anyone help, please?

Thanks in advance

Joomla! 3.10.12
VirtueMart 4.2.0 10905