byte ledPin[] = {4, 5, 6, 7, 8, 9, 10, 11, 12, 13};
int potPin = 0;
int ledDelay = 65;
int direction = 1;
int currentLED = 0;
unsigned long changeTime;

void setup() {
 for (int x=0; x<10; x++) {
  pinMode(ledPin[x], OUTPUT);
 }
 changeTime = millis();
}

void loop() {
 potPin = analogRead(potPin);
ledDelay = map(potPin, 0, 1023, 255, 1);
 if ((millis() - changeTime) > ledDelay) {
  changeLED();
  changeTime = millis();
 }
}

void changeLED() {
 for (int x=0; x<10; x++) { 
  digitalWrite(ledPin[x], LOW);
 }
 digitalWrite(ledPin[currentLED], HIGH);
 currentLED += direction;

 if (currentLED == 9) {direction = -1;}
 if (currentLED == 0) {direction = 1;}
}