Excel masters!

Thank you in advance for your help. I've been working on this all weekend and turning to the experts for some advice.

I work for a media company that uses ratings to measure possible revenue for advertisers. This is done by putting the advertising schedule in with the media sources rating score, adding up the books that align, and then taking the average of those two books. Please note, we add sources together first and then find the average. This prevents me from just averaging everything and then summing the stations that have the same number of minutes in the same daypart. Additionally, if the ratings are lower in the most current book the lower number is adopted instead of an average of the two books.

I've attached a SMALL fake sheet to illustrate what I'm trying to do. I already filled in the top form to assist how the numbers are averaged.

In the sample sheet, Station ABCD and PQRS are running the same number of minutes within the same daypart. So their respective Fall numbers are summed, then Spring numbers summed, and those sums are averaged.
JLKM is running a different schedule that is unique, so it is listed seperately in the top and averaged.
WXYZ's latest number in the daypart selected (F 5a-11p) is lower than the previous score (S 5a-11p) therefore its number is not averaged, rather the lower score is taken.

My ultimate goal is to copy and paste different scores in the lower table, adjust the two columns on the far right of that table and auto populate the data in the top table. Book1.xlsx

Thank you so much for any and all help!

M.