What apps can auto print selected items on packing labels?

[Modern-K9]

We use Print out Designer and it works very well for our order printing needs. We have set up some complex auto prints. However we have hit a road block. Ideas on apps that may work?

All our orders auto print, with what we call packing labels for each product. Our POS orders are not set to auto print, becuase it is not needed. This is where we are stuck. 

POS order, we want to auto print SOME of the items onto packing labels once the order is complete. I can set it up to print the entire order, and pick and choose entire orders, but I cannot seem to find an app that will allow certain products to print and not others on the same order. This has to be automated, and easy, we are a very busy retail store with no time to hand select items or thumb through options.