Update Native AS3 Classes?

Is there any way to update the native AS3 classes short of purchasing a newer version of Flash?

A native class has some additional functionality I’d like to use but do not have access to it currently (I am using CS4). A co-worker using CS5 does have access to the property.

I’m not sure if it’s relevant, but I’m trying access the backBufferLength property of the **flash.net.NetStream **class.

Any idea?