how do i replace delay with millis in this code

Projects Programming
8

i tried using millis. however the servo is not moving randomly after a gap of 2 seconds

int iOldPos, iNewPos = 0;
long previousMillis = 0;
const int interval = 20;

void setup() {
  myservo.attach(3);
}

void loop(){
iNewPos = random(200, 800);
iOldPos = random(800, 2400);
unsigned long currentMillis = millis();

if(iOldPos != iNewPos && currentMillis - previousMillis > interval) 
{
   previousMillis = currentMillis;
    iOldPos = iNewPos;
     myservo.write(iNewPos); 
}
}