Short of using VBA, you'd need to "Use a formula to determine which cells to format." In that formula, add each condition found on the row, and format the cell if the sum >= 3.
In the following example, data is conditionally formatted if it's within the top 20% value per column:
We need a formula that determines if 3 or more data points are within the top 20% per column.
If a number is in the top 20% of a dataset, it's in the 80th percentile. (100% - 20% = 80%). Excel has a PERCENTILE
function, which is just what we need.
=PERCENTILE(A$1:A$15,0.8)
returns the number 8. So any value 8 and above should be highlighted, which we see in the example.
We would get TRUE or FALSE if we compared each value in the A column with the percentile. I've done the same for all columns below, giving us a grid of TRUEs and FALSEs.
Now we need to determine if there are 3 or more TRUEs. This is easy to do, because TRUE is represented as a 1 in Excel, and FALSE is represented as a 0. So we can add the TRUEs and FALSEs per row:
Combine all this work into a conditional format formula, and this is what you get:
=($A1>=PERCENTILE($A$1:$A$15,0.8))+
($B1>=PERCENTILE($B$1:$B$15,0.8))+
($C1>=PERCENTILE($C$1:$C$15,0.8))+
($D1>=PERCENTILE($D$1:$D$15,0.8))+
($E1>=PERCENTILE($E$1:$E$15,0.8)) >= 3
I used the above formula for my example data, so rows with 3 or more highlighted cells get bold numbers and red borders: