do invoice for customer for automatics invoices

do invoice for customer for automatics invoices

I have an application in which I serve clients, I worked a contract between me and the client on a certain date, I want to send the customer invoices that 3 invoices every end of the month how to do that in the Creator, and how to separate his clients from another, because each invoice will be automatically treated, and I want to do these invoices repeated monthly for 3 months from the date of the contract.