XAML Custom Control HELP??

I need to draw the following UserControl in XAML:

The Yellow rectangle needs to rotate 360 degree when I set a property on the control to TRUE to indicate that it is operating...while rotating the yellow rectangle should stretch as needed inside the top ellipse.

I am a beginner and trying to learn Blend to do this but not successful so far... If you have an idea please let me know.

Thank You