ko.bindingHandlers.toggleSlide= {
    init: function(element, valueAccessor, allBindings) {
    var hiddenText = allBindings.get('toggleTextCollapsed');
    var visText = allBindings.get('toggleTextExpanded');
        $(element).click(function() {
        if($(element).is(':visible')) {
            $(element).slideUp('fast');
            if(togText)
                $(element).text(hiddenText);
        }
        else {
            $(element).slideDown('fast');
            if(togText)
                $(element).text(visText);
        }
    });
    }
};

////////////////////////////////////////

then on my button I have

--NOTHING NEEDED--

//////////////////////////////////////


data-bind="toggleSlide, toggleTextCollapsed: 'Show Choices', toggleTextExpanded: 'Hide Choices'