How to add Line Items to a Custom Print?

I have a BP that has 20 line items.  How do I set up my Custom Print to pull the data from the first 10, one a time into my Custom Print?  For example, I have a tab called "Alternates" for a contract that has a data element called "Alternate" that lists the alternate name, and then a data element for  it's "Amount".  I want to add the first 10 alternates (name and amount) sequentially into my Custom Print.  Each "alternate" is in its own line item.  I am guessing I need to first select the tab (alternates) and then