Handling multiresolution

Hi,
I am trying to understand cocos multiresolution system.I’ve read wiki articles but still have some issues.

In appDeleage I set
pEGLView->setDesignResolutionSize( designResolutionSize.width, designResolutionSize.height, kResolutionShowAll );

After that I get borders (as expected).
Why does a touch event is not created when I tap on the borders?
And is there a way to calculate the width of the borders?
Something that would look in pseudocode like

borderWidth = (absoluteDesviceWidth - designResolution)/2