How do I automate my package and shipment process

How do I automate my package and shipment process

Hey, I have a very basic problem regarding automating my package and shipment. My business does not require me to have those modules and manage them currently and since I'm new to zoho I want to start with just the basics. I just need to automatically mark the items from my SO that I convert into a partial invoce/invoice. As soon as the invoice is generated, those items from SO are automatically marked as packed and shipped. 

I know I can do this with a simple Deluge script and Custom Functions but I'm new to this and figuring out stuff myself so wanted help on that.

Thanks,
Het