Colorbox: Show/simulate 'loading' animation for iframe content?

How can I show or simulate (using a fixed timespan) a loading animation for iframe content which is displayed using Colorbox?

What I'd like to achieve is actually a temporary overlay over the if开发者_如何学编程rame content, which disappears when the iframe-content is loaded. Is this somewhat possible?

There is LoadMask plugin that can display an overlay. You will need to control when to show it and when to hide it manually though.