GUI Display Help

Hey everyone, I'm currently working on a game for a class I have and I need just a little bit of help.

This is what the code looks like...

var Cactus : Texture2D; var Cactus2 : Texture2D; var button1clicked=false;

function OnGUI () { if (GUI.Button (Rect (375, 100, 150, 100), Cactus)) { if(!button1clicked) button1clicked=true; else button1clicked=false; }

 if(button1clicked){
    GUI.Box(Rect(375, 210, 315, 300), "");
    GUI.Label(Rect(375, 210, 90, 90),"Cactus");
    GUI.Box(Rect(10, 370, 350, 140), Cactus2);
 }  

}

What I want to happen is when I click another button, the previous button is deactivated.

Does anyone know what the code would look like? All the help would be greatly appreciated! :D