Limit CPU usage of background process if system is busy

At the moment I do the following: When I see that the system load of my Ubuntu server is high, I get the PIDs of specific currently running background processes and start cpulimit with the PID. When the system load gets lower, I kill cpulimit, so that the background processes can run faster. When the load is still too high, I also kill cpulimit and start it again with a lower limit for the process. I repeat this until the background processes are done after a few hours. But it gets very annoying to do this manually every day, so I would like to know if there is a way to automate this.