Incoming Purchase invoices sometimes only come with total before sales tax

Incoming Purchase invoices sometimes only come with total before sales tax showing on each individual line and grand total at the end. So there fore to to check each line is correct the Vat amount has to be set to 0% on each line. It would be great to have a Column with a sub total without Vat.

purchase code / product / job / qty / descript / rate / vat rate/ vat / total
/18.34 / 8.50 / 20% / 31.18 /187.07

I would like to see

/ qty / descript / rate / sub total no vat / vat rate / vat / total
/18.34 / / 8.50 / 155.89 / 20% / 31.18 / 187.07