Schedule Lines and Goods Issue Dates

Hi Gurus,

I am trying to write a report which will show all the planned goods issue dates for orders. Question : when a delivery document is created and it has a different planned goods issue date than an existing schedule line, will a new schedule line be created or copied into or will nothing happen. I guess what I am trying to ask is can I just go read the schedule line or I must go into delivery document to get the latest planned goods issue date.

Thanks.