ReScaling with easing?!

Hello, I use a piece of code that is supposed to enlarge a small tab in a larger area of information (all hover). The code works but also by reducing the value of magnification tab moves from position to position "unfolded" instantly ... GUI does not run to the enterFrame?

 private float _Wacceuil = 40;//valeurs références par défaut
     private float _Hacceuil = 50;
     private float _WacceuilOFF = 40;//valeurs références d'origines, position plié
     private float _HacceuilOFF = 50;
     private float _WacceuilON = 100;//valeurs références d'origines, position déplié
     private float _HacceuilON = 250;
 
 GUI.Button(new Rect(0, 60, _Wacceuil, _Hacceuil), "Acceuil");    
 if (Input.mousePosition.x>0&&Input.mousePosition.y<Screen.height-60 &&
     Input.mousePosition.x<0+_Wacceuil &&
     Input.mousePosition.y>Screen.height-60-_Hacceuil)
     {
             while(_Wacceuil < _WacceuilON)
             {
                 _Wacceuil += .1f;
             }
             while(_Hacceuil < _HacceuilON)
             {
                 _Hacceuil += .1ff;
             }
         }
         else
         {
             if(_Wacceuil > _WacceuilOFF)
             {
                 while(_Wacceuil > _WacceuilOFF)
                 {
                     _Wacceuil -= .1f;
                 }
             }
             if(_Hacceuil > _HacceuilOFF)
             {
                 while(_Hacceuil > _HacceuilOFF)
                 {
                     _Hacceuil -= .1f;
                 }
             }
         }