Allow positioning of the ball at the start/on a 'sticky' bat

At the beginning of a level - or when the ball is on a 'sticky' bat, I'd sometimes like to be able to set the ball off from a point other than the centre of the bat. This could be achieved by allowing the scroll-wheel to move the ball along the bar (forward=left/right, back=right/left) or by having the right mouse-button scroll the ball along the bat. I imagine the ball would fire off at an angle either as if it had hit at 90-degrees (for the beginning of the level) or as if it had hit at the same angle as where it originally landed (for a 'sticky' bat).