I am not sure that @julian or @uday_guntupalli are interpreting your question properly. What I believe you are asking, is "How do you reference the selected rows for a specific column, or set of columns.
JMP allows one to access any given cell by the column name or number, and the row number. Selected rows can be accessed by getting back from JMP a list of the rows that have been selected. Below is a little script that shows some of the uses
Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA\Big Class.jmp" );
dt << select where( :Age > 15 );
// Examples
Show( dt << get selected rows );
Show( :name[dt << get selected rows] );
Show( :Name[(dt << get selected rows)[2]],
:age[(dt << get selected rows)[2]] );
Jim