Change Freeform redirect URL according to checkbox field
This should be doable. If you have a field in your formatting template with the name formReturnUrl, when checked, it would override the Freeform return URL. You'd likely need to manually hardcode this into your form template code though:

&lt;input type="checkbox" name="formReturnUrl" value="{{ siteUrl }}freeform-demo/bootstrap/my-url" /&gt;