int StepsPerRevaloution=2048;
 Stepper mystepper(StepsPerRevaloution, 8,10,9,11);
int motspeed=10;
int dt=500;
int buttonpin=13;
int buttonval;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
mystepper.setSpeed(motspeed);
pinMode(buttonpin, INPUT);
digitalWrite(buttonpin, HIGH);
}

void loop() {
  // put your main code here, to run repeatedly:
buttonval=digitalRead(buttonpin);
Serial.print("button value is ");
Serial.println(buttonval);

mystepper.step(StepsPerRevaloution);

if (buttonval==0) {
mystepper.step(-StepsPerRevaloution);
}
}