Is there a program or setting on the AS website that would notify me if/when I could use a GGU on a certain flight?

I had to rebook this flight as I need to stay in LIS longer and AA could not do it without adding a $1,500 extra fee. In the process I lost my Premium aisle seat on the SEA-PHL leg but saved $313 by returning LIS-MAD-DFW-ABQ via IB.