Combo box Keystroke script

// Custom Keystroke script
(function () {

    if (event.willCommit) {
        return;
    }

    var f1 = getField("s");
    var f2 = getField("gr");
    var f3 = getField("b");

    // Get the export value of the selected item
    var sh = event.changeEx;

    // Show/hide the fields
    switch (sh) {
    case "1" :
        f1.display = display.visible;
        f2.display = display.hidden;
        f3.display = display.hidden;
        break;
    case "2" :
        f1.display = display.hidden;
        f2.display = display.visible;
        f3.display = display.hidden;
        break;
    case "3" :
        f1.display = display.hidden;
        f2.display = display.hidden;
        f3.display = display.hidden;
        break;
    default :
        // If some other combo box item is selected
        // add additional code
        break;
    }

})();