Turn page, smooth rotate

Hi everyone,

I ran again into something I am yet to understand and learn how to achieve : smooth rotate an object from an angle to another. What I want to do in this case is have a button rotate (turn) a page (game object); ideally it should have an array of pages but for now I want to get around this smooth rotate thing. A page should slowly rotate 180 degrees when I press a button, with an exposed speed variable.

Here's what I use and doesn't really do the trick:

 //turn
   
 
 var page1 : GameObject;
 var page2 : GameObject;
 var page3 : GameObject;
 var smooth = 2.0;

 function OnGUI () 
 
 {
 
      if (GUI.Button(Rect(0,0,50,30),"Next"))
             {
             page2.transform.Rotate (0, 0, -180);            
             }
 
       if (GUI.Button(Rect(0,200,50,30),"Previous"))
             {
                 page2.transform.Rotate (0, 0, 180*smooth*Time.deltaTime);            
             }
 
 }