Creating VBA UserForm for Multiple Invoice Lines

[glitch0x6]

Hi, This is going to be a long one, so brace yourself. I am fairly new to VBA so this is a project. I am trying to create an easy to fill out form to help my company track inquiries. There is going to be a master sheet where all this information is compiled. What I need to be able to do is enter multiple pieces of information (quantity, size, grade, etc) for each invoice line, but have the ability to produce multiple lines that link to a particular sales order number. Also, since the number of lines vary per customer (some order 2 different things others order 10), I need my Userform to be able to duplicate the data entry form multiple times without having to refill out customer info for each individual line. Is this even possible? If it is possible, can you point me in a direction where I can learn how to do it? I already built a sheet that does most of this, but I don't want one of the other sales people accidentally messing up the master file and figured a Userform would be best.