iPhone UIButton custom animation

I would like to create a custom animation on an UIButton. The animation should be similar to a progress bar and when the user presses the button, it should start. My UIButton is an custom one, added wit开发者_C百科h the Interface Builder and has a custom background.

Is there a way to create this kind of animation? I am having problems since the custom background is an image with shadow and other effects, like glow and emboss.

Thank you!

Andrei for this you'll have to change the background images of the button in some function that is called by NSTimer initialized in the IBAction of that button.

With this approach I have did this in one of my application