It is common to blame these kinds of things on Southwest IT for the unfriendly web site. I have come to believe that at least some of the reason is to obscure information to make it difficult for customers in order to enhance profits. This is a prime example. It is difficult to rebook a lower fare if you can't confirm the original price.
I'm not sure but I think automating the process may violate the T & C of the website.
You may not use any deep-link, page-scrape, robot, crawl, index, spider, click spam, macro programs, Internet agent, or other automatic device, program, algorithm or methodology which does the same things, to use, access, copy, acquire information, generate impressions or clicks, input information, store information, search, generate searches, or monitor any portion of the Southwest Airlines sites or Company information.