自定义控件x：类问题和动画

I am trying to create a Menu Custom Control that contains some Animations to make things look a little more "Fluid". This is where I am running into Problems, I would like to have the Width of my Custom Control be driven by a animation to emulate the expanding of the menu. I can achieve this by using Triggers in the Template but using this method I can't seem to find a way to bind the "to", I had read that this isn't allowed because of Thread Safety so I figured I would just use the "Click" event and do the Animation in the Code Behind.I am trying to create a Menu Custom Control tha