I would recommend looking into a PID controller in order to get more accurate results. The loop can be used to drive straight by calculating the difference in right and left encoders and adjusting accordingly. The controller can also be used to travel accurate distances to prevent over or undershooting.
I would recommend looking at this link: https://www.vexforum.com/t/a-pid-controller-in-robotc/20105
and this as well: https://www.vexforum.com/t/pid-help/35429/5