VAT good and Non VAT goods on a single invoice in iSupplier ?

On most of the invoices there are Vat and non-vat goods.  On I-Supplier at the moment there is no function for the suppliers to enter an amount that is to be inclusive of Vat and a separate line for their non-vat goods.   The only way currently for them to submit invoices through I-Supplier would be generating a separate invoice for the VAT goods and Non-Vat goods but as you can understand this could be very difficult with the amount of goods ordered each time.

Is it possible to set up on I-Supplier a way of where they could enter a separate amount for the Non-vat and VAT items to allow them to submit each invoice in one entry?