[CLOSED] Minimize window created in another desktop window

[CarWise]

I'm using this code to create another window from a desktopwindow:

function CreateDesktopWindow(title, id) {
            if (top.winWijzigBestuurder) {
                top.winWijzigBestuurder.destroy();
            }
            var onTop = new Ext.WindowGroup;
            onTop.zseed = 10000;
            var win = new top.window.Ext.Window({
                id: 'winWijzigBestuurder',
                title: title,
                width: 500,
                height: 520,
                Icon: "UserEdit",
                maximizable: false,
                minimizable: true,
                constrainHeader: true,
                manager: onTop,
                autoLoad: {
                    showMask: true,
                    mode: "iframe",
                    url: "url.aspx"                }
            });
            win.show();
        }

The window opens like it should. But..

I would like to minimize this window also to the desktop taskbar. But nothing happens when clicking the '-' button

How do I accomplish this ?

Martin