How to throttle a backup so not interferes with use of computer?

Backup & Restore 14 Free
Windows 7 Home Edition x64 SP-1

My computer is in use at various times of the day: morning, afternoon, evening, night, anytime. I found no means of setting the process priority of the backup job. That means if I am using the computer and the backup starts, responsiveness could crawl to make my computer unusable to me.

No matter when I might schedule a backup job, I could be using my computer at that time. Pick any time and, yep, I will sometimes be using the computer at that time. I need backups to be scheduled to ensure they get done. Anytime users are relied upon to perform backups means they are unreliable - users slack off, are away, forget, or get too busy.

If backups cannot be made to run in low priority then I won't be running them (with this software). Backups do not have priority over my use of my computer.