I feel like there could be a more efficient way, but I do have this working on a table where there are more than 3 entries for each of the customers, A, B, and C…
The Customer control selector is named: SelectCustomer
And here are the formulas used:
Data Modified Column:
=Modified(thisRow)
Rank Column:
=Rank(thisRow.[Data Modified],thisTable.[Data Modified])
Rank List Column:
=Filter(thisTable,Customer=SelectCustomer).Rank.Sort().Slice(1,3)
And the Filter for the whole table:
=(Customer=SelectCustomer) AND Rank.Contains([Rank List])