I am excited about this project because it has many similarities to a project I developed for tracking athletes, selecting teams, weighting recent performance against personal bests. I have been working with Access since it was first released. I advise against MS SQL (personal edition) - only the Enterprise edition is solid, and would be overkill. Good open source SQL solutions if you want to go down that line in the future. But you seem comfortable in Access and I would recommend sticking with it.
Some interesting edge cases - what if there isn't 6 race results to calculate an average - use the 5 (or 4) and flag it as such? Your decision of course.
You seem knowledgeable, so I would provide well commented code you could make small tweaks yourself.
For your test question, I would ensure the data had the placing as a field (even if that is derived from data order). Fractional lengths would need to be converted to decimals (trivial if required). Final result would be:
"ID","Race","Name","Place","Distance Beaten","Adjusted Weight"
1,1,"Horse A",1.00,0.00,110.00
2,1,"Horse B",2.00,2.00,116.00
3,1,"Horse C",3.00,1.00,119.00
4,1,"Horse D",4.00,1.50,123.50
5,1,"Horse E",5.00,1.75,128.75
6,1,"Horse F",6.00,4.00,140.75
7,1,"Horse G",7.00,0.50,142.25
8,1,"Horse H",8.00,2.00,148.25
Code can be viewed at [login to view URL]
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