Cron cannot stop any jobs, only execute them. So you have to create to Bash scripts.
The first one to start your job and record the PID in a file.
The second one to read the PID and kill the job.
You should check if the PID exists before you start another instance. And take appropriate action.
The normal location to store PID files is /var/run/
Both are started from Cron but have a different purpose.
Alternatively you can follow a more crude way if the application's name is unique. You would start it normally and end it with:
The -f makes kill to terminate any program containing foo.
Then you don't have to write the Bash files. You don't need to record the PID and the kill command can be configured in cron. But it is not very elegant. If you issue the kill command as root you'll kill the programs for all users.