Holding GUI Button Touch to Rotate Object

How to make an object rotates if you hold the GUI Button ? For instance : Turn Left Button, if you pressing (hold) turn left button, the object will rotates to the left till you lift your hand (TouchPhase.Ended).

Here's my script

 if(GUILayout.Button(someTextures[10])){
     if(Input.touches.Length > 0 && Input.touches[0].phase == TouchPhase.Began){
         rxz = -1 * 10;
         rxz *= Time.deltaTime;
     }else if (Input.touches.Length > 0 && Input.touches[0].phase == TouchPhase.Ended) rxz = 0;
     //cnt.isPressing[1] = true;
 }
 rxz is float = 0. at function update() prnt.transform.Rotate(0,rxz,0);

I also have a problem in launching the object for the first time. For Instance : I hold the GUI Button, it was directly become 1.50 (it should be clamping from 0 to 1.50) i don't know how to say.here's my another script

     if(isPressing[0]){
         if(Input.touches.Length >0){
             if(Input.touches[0].phase == TouchPhase.Began){
                 start = Time.timeSinceLevelLoad;
                 gui.ShowMe(true);
             }else if(Input.touches[0].phase == TouchPhase.Ended){
              end = Time.timeSinceLevelLoad;
              gui.ShowMe(false);
              hint.ShowHint(power.ToString("f2"),1.5, false);
              StopMe();
              force = power*speed;  // here you compare the 2 values I had to multiply by 20 to get it up (that's what she says) but you might have to alter this eqution to get what you want  
               if(throwingSFX ){
                       audio.Stop();
                       audio.clip = throwingSFX[Random.Range(0,throwingSFX.length)];
                       audio.Play();
               }
             }
         }
     }

from another GUI Script if(GUILayout.Button(someTextures[8]))cnt.isPressing[0] = true;