Can I use a Flex Project to instanciate a sprite that loads an swf?

Can I use a Flex Project to instanciate a sprite that loads an swf?

I have an ActionScript project with a Sprite that loads an SWF and
executes it. I would like to create a Flex Project (which is what I am
familiar with) to instanciate that Sprite. I tried but I get the error:
//code to add a Canvas into the WindowedApplication->Launcher
var container:Canvas = new Canvas();
container.addChild(loader);
this.launcher.addChild(container);
VerifyError: Error #1053: Illegal override of activate in
mx.managers.SystemManagerProxy.
I wanted to use that Flex Project to have a progress bar assign the loader
in the Sprite as the source. Finally, when the loader would be done I
would execute the SWF loaded. Is this possible? If not then what would be
the best alternative?