Duty cycle of 20% on a motor for 1 second and stop.

Hello members!

I am trying to build a robot car for my highschool project and I'm stuck on this problem. I was able to "hack" into the electronics of the car and connect the wires that move it left and right onto the arduino, and I was also able to make it go left and right. However, the only problem was that it turned left too fast, or turned right too fast. So I thought of adding a duty cycle to it of 20% to "reduce" the voltage and make it turn slower. I just need some help because when I add in the code for the duty cycle, I can't make the motor stop moving. Here is my code, just need it to move for 1 second and then stop moving. I tried so many things, I don't know how I can make it stop moving.

int left=12; //apply 1 to turn left
int right=11; //apply 1 to turn right

//This is the part of the code that works on reducing the speed of the motor
digitalWrite(left, LOW);
digitalWrite(right, HIGH);
delayMicroseconds(200); // Approximately 20% duty cycle @ 1KHz
digitalWrite(right, LOW);
delayMicroseconds(1000 - 200);

Congratulations. You have invented Pulse Width Modulation, or PWM for short.

Read up on the analogWrite() function to see how to vary the duty cycle of an Arduino PWM pin between what the motor will see as 0 volts and 5 volts when the output varies from 0 to 255.