<div>
    <button id="btn" label="Rename" onClick="onClick()"/>
    <textbox id="tbx" />
    <portallayout>
        <portalchildren>
            <panel id="panel" title="Change Me" border="normal">
                <panelchildren>
                    <div style="display:block;" width="400px" height="300px"/>
                </panelchildren>
            </panel>
        </portalchildren>
    </portallayout>
    <zscript>
        public void onClick() {
            panel.setTitle(tbx.getValue());
        }
    </zscript>
</div>