Maybe this is what you are trying to do.
dt = Open( "$sample_data/big class.jmp" );
ColumnList = {"height", "weight", "age"};
ValueList = {13, 128, 60};
For Each( {col}, ColumnList,
For Each( {ValueItem}, ValueList,
dt << select where( As Column( dt, col ) == ValueItem, Current Selection( "extend" ) )
)
);
or even this
dt = Open( "$sample_data/big class.jmp" );
ColumnList = {:height, :weight, :age};
ValueList = {13, 128, 60};
For Each( {col}, ColumnList,
For Each( {ValueItem}, ValueList, dt << select where( col == ValueItem, Current Selection( "extend" ) ) )
);
(It might make sense with your data, but with big class it doesn't make a lot of sense to select rows where height or weight or age are 13, or where height or weight or age are 128, or where height or weight or age are 60. Just using it to try to match what I think you mean.)
Craige