how to generate invoice on project event with zero dollar

Hi,

I would like to create an milestone invoice in project billing. There will be multiple project events with same date and some of the events are zero dollar value. Basically whenever there is no adjustment on invoice, there will be event with zero value with description as same description should reflect in customer invoice.

Example

Project Event details

Project	Date	Event Type	Amount	Description
15248	31-Jul-2016	Manual	30000	Milestone billing for July-16, $1000 @ 30 Days
15248	31-Jul-2016	Manual	0	No Down time for July-16, $1000 @ 0 days
15248	31-Jul-2016	Manual	-1000	Customer items used.

Total                                                                                               29000

Thanks

Rob