How to return from the last case to the first

The whole thing is that i want to make a reload code for my ammo.

Example Code

   var ammo1:GUITexture;
    var ammo2:GUITexture;
    var ammo3:GUITexture;
    var AMMO = 3

    function FixedUpdate()
    {
    switch(AMMO)
    {
    case 1:
    guiTexture.texture = ammo1;
    break;
    }
    case 2:
    guiTexture.texture = ammo2;
    break;
    }
    case 3:
    guiTexture.texture = ammo3;
    break;

    case 4:
//return to case 1.
    break;
    }
    if(Input.GetButton("Fire1")
ScriptName.AMMO -= 1;
    }

U could make the last case = the first one ie:

case 4:
 AMMO = 1;
break;

Or replace 4 with 0 since u run OUT of ammo.