AR: Autoinvoice import - create summary invoices

All,

We are importing transactions from a legacy system. The information is in detail and could result in thousands of lines per customer. We would like autoinvoice to not only group the transacions per invoice we would like it to summarize the lines. 

Is this possible? and if it is possible, what exactly do we need to do?

This is an example of what we would like autoinvoice to do:

Customer X imports the following transactions:

 Item A      Item B 

 Item A      Item B 

 Item A 

All detail is imported and then we would autoinvoice to create a summary invoice like the example: