Does this sound like what you want to do?? Bearing in mind this done with a cd-r, not a cd-rw as gonaads pointed out! <NERO Burning Rom and NERO InCD are two different programs>
From NERO Burning ROM Help:
Multisession CDs are advisable, say, when making a weekly Backup of a number of folders on a CD.
When an ISO compilation is created the required folder is written to the CD in every new session. Since only a few files may have changed, writing the entire folder again would have the following disadvantages:
Burning would take an unnecessarily long time because redundant data are being written each time.
Valuable CD space would be wasted as the same data is copied a number of times.
With a CD-R, data can only be written to a CD but cannot be deleted or changed, so the following procedure is used with Multisession CDs:
Instead of writing the unchanged data again with every session (i.e. every backup procedure), Nero only writes cross-references to a previous CD track which contains the unchanged file. Only the changed files are completely re-written.
By activating the two checkboxes 'Replace files in compilation' and 'Add new files to compilation' in the 'Options' section you will ensure that this actually happens.
Of course when individual sessions are linked to one another there must be some way of ensuring that the tracks (which have a definite connection to an existing CD) are not written to another CD by mistake. This would make all files with references outside the tracks unreadable later on! For this reason Nero checks that the correct CD has been loaded for burning. If it hasn't, then the CD that has been loaded in error is ejected.