Flash CS6 - How to hide a symbol in flash animation?

hi ,
i want to animate a logo . i am trying to achive something like this , please try almeerepc.com. I did achieve the same with have a white image over the gear wheel.However , when i exported it as stage as transparent , the white area was seen . Is there a way to animate ,hiding a part of the wheel ,like say alpha still making the wheel rotate ?
please help .


thanks in advance .

Why don't you just ry to set visibliity to 0?