how to force changing the resolution to another different from default

Hi,
My problem results from a small icon. The BB10 alpha device is 1280x768 and my 16x16 icon is very small when displaying the original pixel size on the screen. I know there are some ways to make it bigger on the screen and I choose to scale down the screen resolution like 1024x600. But how can I change it flexible when needed? I check the HelloCpp sample that it change EGL frame size in main.cpp but i wanna change it dynamically in helloworld.cpp like this
@
//helloworld.cpp
HelloWorld::init()
{

CCDirector::sharedDirector()->getOpenGLView()->setFrameSize(1024, 600);

}
@
This seems doesn’t work and the resolution no change. Of course if I change the code in main.cpp it definitely works. So can I dynamically change the EGL view resolution in difference scene or it can only be fixed for all scenes in one application?
Thanks.

regards,
pigling