show/hide GUI.box with a GUI.button

I did some research but couldn't seem to find anything significant. Here's what I have so far:

 var showInventory = false;
 
 function OnGUI () {
     if(GUI.Button(Rect(210,80,35,30), "Open")){
     showInventory = true;
     }
     if (showInventory) {
     GUI.Box(Rect (10,50,315,300), "Inventory"); // x, y, w, h
     }
 }

When the user clicks the GUI.Button, the GUI.Box should popup, when he clicks it again, it should disappear and etc... (a toggle button basically).