Combining Invoice?

I was wondering if there's any way to combine invoices to make one single invoice so I can bill my clients Monthly?

OR...

Is there a way to add a little note section within the invoice next to the Product Name?

We sell photography services, for example, one of our product name is "Custom Photo Tour", we may sell this service 10 times to the same clients, but on a different day.
I want to be able to say:

Custom Photo Tour - Oct 4, 2007
Custom Photo Tour - Oct 5, 2007

in one single invoice and bill my client monthly.

Now the only way I can think of is to change the product name, to have each date, a new product name. But this will be chaos!!! And I can't figure out a way to customize any type of notes next to the product name in the invoice.

I also don't mind creating multiple invoices after each assignment. If there's a way to combine all these to one single invoice, it would be great. Any idea?