First get the indices or names of the columns you wish to find the values from and then either use Min to get minimum value and Loc() to find the value OR use Loc Min() to find index and then that index to find the minimum value. Below is example using Loc Min to get index and then the value
Names Default To Here(1);
dt = Open("$SAMPLE_DATA/PopAgeGroup.jmp");
// get either index or name of columns of interest
cols_of_interest = Filter Each({col_name}, dt << Get Column Names(Continuous, "String"),
!IsMissing(Regex(col_name, "^(Portion|F Rate).*[\d+]$"))
);
dt << New Column("MinIdx", Numeric, Continuous, << Set Each Value(
Loc Min(dt[Row(), cols_of_interest])
));
dt << New Column("MinVal", Numeric, Continuous, << Set Each Value(
dt[Row(), cols_of_interest[:MinIdx]]
));
Also if you have no need for formulas, it is better to not use them and rather use << Set Each Value.
-Jarmo