Add a file to a CD-RW with CD/DVD creator

First, I must tell to the community how impressive is the Feisty release! Fine work and so pleasant to use.

The problem.
How can I burn a new session on a previously burnt CD-R or CD-RW?
CD/DVD creator seems to offer only the possibility to erase the CD/DVD before burning a session.

If it's not possible with this tool, what is the recommanded application to burn in multisession?

Thanks