Use qp_price_list_PUB.process_price_list to add new price break line to existing price break header

This code below will create a new Price Break Header Line and Price Break line for item_id 161140, detailing Qty 1 to 10 is $10.

After this has been run successfully, how do I then add an additional Price Break Line to the now existing Price Break Header Line?

For example, I want to add an additional line showing Qty 11 to 20 is $9.

Thanks!

Chad

l_price_list_rec.list_header_id                                    := P_Input; --header id of created price list
   l_price_list_rec.list_type_code                                    := 'PRL';
   l_price_list_rec.currency_code                                     := 'USD';
   l_price_list_rec.operation                                         := qp_globals.g_opr_update;