Is there a way to load dynamically content inside a window created with Ext.air.NativeWindow

For instance, my main window has 2 buttons.

I'd like that when you click on button 1, inside the window (eg : inside <div id = "content"></div>) page1.html is loaded
the same when you click on button 2, inside the window page2.html is loaded

Both of these pages are part of my application and are in the same directory of the main window

I tryed to achieve that by using Ext.Ajax.request but this doesn't works because of sandbox limitations, the html is loaded but css and js aren't

I also tryed to look at air.HTMLLoader but I couldn't find a way to place new content inside a particular div, however this loads successfully css and js

Finally the only working way I have found is to use an iframe, but I'm looking for a better way to do that if it's possible.

Thanks for any help