I am arranging a trip between North Asia (e.g. ICN) and South America (e.g. RIO). No matter how I make through the journey, I would have to transfer either in Europe (e.g. LIS) or in North America (e.g. LAX). Therefore, I hope to make a stopover in one of the cities (e.g. LIS or LAX) during my trip. However, when I tried to use the multi-city search options on United.com,a total number of 170000 miles is calculated and each segment of the itinerary can be located (i.e. ICN-LIS plus LIS-RIO plus RIO-ICN). Unfortunately. it showed "error" when I intended to purchase the ticket at the final phase. I am wondering if such an itinerary violates any of the Mileage Plus award rules. Thank you very much for your help in advance!