1. have the catalog created on 10G
2. have oracle 9i installed on the 10G server
3. Enable the remote login to the 9i servers to authenticate with the password file, and enable the remote_login option on the databases.
4. Write a shell script that would set the oracle environment accrodingly to the database it is backing up.
5. Create a scheduler script to where you call the backup script with the database names in the order you want them to be backed up. Remember not to put them in the background
6. In your crontab call this scheduler script and put it in the background.
So what will happen is that when the cron job executes the schedulter script, it is forced to execute and finish the first job before it stats the next. This would help you to achieve the order you would want.
On the other hand if you would like to have the setup on the local server 9i side, have the 10G installed on the local server side, start the listener under 10G on the local server and configure all your remote dbs to be remote accessible with the sysdba privs. Then schdule the jobs from the local server crontab to do the backups.