How to copy a section of a field?

How can I use an action to take a section from a field, by instructed a start point or end point.?

For example, if I have the comments field filled with genres & other such info like this:

"rock"indie rock"folk"cbr"320"rel2004"

How would I copy the "cbr"320" out if I want to use it in another field?

You can use an action of the type "Guess values" for COMMENT.
Enter as guessing pattern
%dummy%cbr"%anotherfield"rel%dummy%"

Convert | Tag - Tag | ALT+5
Field:
ANOTHERFIELD
Format string:

$regexp(%COMMENT%,'^.*"(cbr)"(.+?)".*$','$1 $2')

Preview
cbr 320

Begin Action Group Test_2013#20131215(1)

Action #1
Actiontype 5: Format value
Field ______: ANOTHERFIELD
Formatstring: $regexp(%COMMENT%,'^."(cbr)"(.+?)".$','$1 $2')
End Action Group Test_2013#20131215(1) (1 Action)

Begin Action Group Test_2013#20131215(2)

Action #1
Actiontype 7: Import tag fields (guess values)
Source format __: $replace(%COMMENT%,'"cbr"','"cbr"cbr ')
Guessing pattern: %DUMMY%"cbr"%ANOTHERFIELD%"%DUMMY%
End Action Group Test_2013#20131215(2) (1 Action)

DD.20131215.2105.CET