export bitrate and VBR fields to a csv file

Hi,
I'm trying to insert the BITRATE and VBR fields into a csv export file, but its not working using:
%bitrate% or %vbr%

How can I export that sort of data on a csv file?

SOLVED***
inserted as %_bitrate% and %_vbr%

The correct names are %_bitrate% and %_vbr%