PN:Transaction Type needs to be the same to group Invoices?

On the lease billing tab the transaction type is a required field, however, the accounting used by PN default to the accounts that are entered on the accounts distribution tab of the billing tab.  If you have multiple billing lines they need to all have the same transaction type to be grouped on one invoice.  Does anyone know a way to use different transaction types and have the multiple lines group.  Also does anyone know how to have PN use the accounting behind the transaction type rather than the account distribution tab?

Thanks.

Erin Johansson