Close GUI on button click?

[Jimbo33]

Hi,
I want my GUI to close when the player presses a button...
Here are the two parts of my GUI Script about the button I want
to close the whole GUI:

    new GuiButtonCtrl("ClassSelect_Button3") {
      profile = GuiBlueButtonProfile;
      text = "Swordsman";
      width = 80;
      x = 10;
      y = 200;
    }

...

function ClassSelect_Button3.onAction() {
//Stuff
}

Please help, all I need is the command to close everything and where to put it, thanks