I was trying to get a column's value as given below which does not work. I have checked variable substitution option in Extractor Properties.
swing/table/row\[cell='${ipadd}'\]/cell[8]
and, how to introduce backslash substitutions for the command:
swing/table/row[cell='[query BTS_data col2(3)]']/cell[8] (Getting cell value from another query here)