Create Invoice Lines from completed appointment

I have a customer that manages their business by setting up appointments and then billing for completed appointments.

I want to be able to programmatically process all appointments that were completed during the prior month (or a given period of time) and create a customer invoice plus an invoice line for each appointment (with details and notes from the appointment record).

Is there a plug-in available to do something like this (or a published piece of code that I could use with CRM in the cloud)?

Thanks

Joe

Joe