How to swap CSS in Sencha Touch

I need to swap the css for my Mobile application done in Sencha Touch.

At the moment I=m not obtaining any result. Could you tell me how to do it?

Thanks

I solved the issue using this code...

var accessibilityButton = {
                xtype: 'button',
                ui: 'custom-btn-confirm',
                maxWidth: '360px',
                centered: true,
                flex: 1,
                scope: this,
                style: 'color: #ffffff',
                text: 'Active Accesibility',
                ui: 'custom-btn-confirm',         

                handler: function changeStyle() {
                    // Swap the CSS for Accessibility
                    var i, a, url, btn;
                    for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
                        if(a.getAttribute("rel").indexOf("style") != -1) {
                            url = a.href;
                            btn = document.getElementById("ext-element-114");

                            if(url.lastIndexOf('app.css') !== -1) {
                                a.href = 'resources/css/app-accesibility.css';
                                btn.textContent = "AAAA";
                            }
                            else {
                                a.href = 'resources/css/app.css';
                                btn.textContent = "BBBB";
                            }
                        } 

                    }

                }

            };