How can I obtain the serial number of the column where the cursor resides using a script?

[#1]

Let's say I select a cell in column 4
The following code only gets the specific column name, not the serial number of the column :4

dt=Open("$SAMPLE_DATA/Big Class.jmp");

aaa=(dt<<get selected columns)[1];

Thanks!

[#2]

ab=(dt<<get selected rows)[1];

？？

[#3 · Accepted solution]

Contains( dt << get column names( string ), aaa << get name );