KnockoutJS - How to reassign URL when checkbox is checked vs. unchecked

I want to assign an URL in a function everytime a checkbox is checked. But I would also like the URL to be reassigned its initial value when the checkBox is unchecked. I was able to create the code below from the following thread, but the URL is not reassigned when I uncheck the box. Sorry I am new to KnockoutJS and to JavaScript in general.

HTML

   <input type="checkbox" name="myCheckBox" data-bind="checked:isChecked, click: setUrl">Search Supplier<br>

JS

  searchShippingCodesUrl = '/Parteners/Search';
...
...
ischecked: ko.observable(false),
        setUrl: function () {
                searchShippingCodesUrl = '/Suppliers/Search';
                return true;            
        },

Thank you for your time.