Golf Handicap calculator

Hello Everybody

I'm John Stevenson & This is my first time posting here.
I run a Design & Print business in Glasgow so my problems are normally more Creative than Mathematical.

However, I'm going on a small golf tour to Turkey this year and have been trying to devise a Handicap Calculator but can't get the right formula

Spreadsheet is attached in case anybody can help.
Handicap Calculator.xlsx
Specification is as follows:
8 people
Names and Handicaps to be entered manually
5 rounds of golf
scores to be entered manually using Stableford points golf system
Total score for 5 rounds to be calculated by the program
Average score for each round (across 8 players) to be calculated for each round
Difference to the average to be calculated for each player, at the end of each round
New Handicaps to be calculated by the program at the end of each round
For players whose score is 1 point better or worse than the average, no handicap change. i.e. if the average score is 36, players scoring 35, 36 or 37 will not have their handicaps changed. This will be called the buffer zone.
For players whose score is better that the average, their handicap is to be decreased by 0.5 for each 1 point their score is better than the buffer zone.
For players whose score is worse that the average, their handicap is to be increased by 0.5 for each 1 point their score is better than the buffer zone.