int led = 13;
int poteni = A0;

unsigned long pMillis;
int interval;

void setup() {
  pinMode(led, OUTPUT);
  pinMode(poteni, INPUT);
}

void loop() {
  int interval = analogRead(poteni);
  unsigned long cMillis = millis();

  if (cMillis - pMillis >= interval) {
    pMillis = cMillis;
    if (!digitalRead(led))
      digitalWrite(led, HIGH);
    else
      digitalWrite(led, LOW);
  }
}